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The Journal of Neuroscience, June 1, 2002, 22(11):4600-4610
The Rostral Raphe Pallidus Nucleus Mediates Pyrogenic
Transmission from the Preoptic Area
Kazuhiro
Nakamura1,
Kiyoshi
Matsumura2,
Takeshi
Kaneko3, 4,
Shigeo
Kobayashi2,
Hironori
Katoh1, and
Manabu
Negishi1
1 Laboratory of Molecular Neurobiology, Graduate School
of Biostudies, 2 Department of Intelligence Science and
Technology, Graduate School of Informatics, 3 Department of
Morphological Brain Science, Graduate School of Medicine, and
4 Core Research for Evolution Science and Technology, Japan
Science and Technology, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan
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ABSTRACT |
Fever is the widely known hallmark of disease and is induced by the
action of the nervous system. It is generally accepted that
prostaglandin (PG) E2 is produced in response to immune
signals and then acts on the preoptic area (POA), which triggers the
stimulation of the sympathetic system, resulting in the production of
fever. Actually, the EP3 subtype of PGE receptor, which is essential for the induction of fever, is known to be localized in POA neurons. However, the neural pathway mediating the pyrogenic transmission from
the POA to the sympathetic system remains unknown. To identify the
neuronal groups involved in the fever-inducing pathway, we first
investigated Fos expression in medullary regions of rats after central
administrations of PGE2. PGE2 application to
the lateral ventricle or directly to the POA strikingly increased the
number of Fos-positive neurons in the rostral part of the raphe
pallidus nucleus (rRPa). Most of these neurons did not exhibit serotonin immunoreactivity. Microinjection of muscimol, a
GABAA receptor agonist, into the rRPa blocked fever and
thermogenesis in brown adipose tissue induced by intra-POA as well as
by intracerebroventricular PGE2 applications. Furthermore,
neural tract tracing studies revealed a direct projection from EP3
receptor-expressing POA neurons to the rRPa. Our results demonstrate
that the rRPa, which has never been associated with the fever
mechanism, mediates the pyrogenic neurotransmission from the POA to the
peripheral sympathetic effectors contributing to fever development.
Key words:
fever; raphe pallidus nucleus; preoptic area; prostaglandin E2; EP3 receptor; brown adipose
tissue; thermogenesis; autonomic nervous system; GABA; thermoregulation
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INTRODUCTION |
Fever has been one of the most
widely known hallmarks of disease since ancient days (Atkins and Bodel,
1972 ), and important roles of fever have been indicated in various
pathological states (Atkins, 1960; Kluger, 1991). In the generation of
the febrile response, prostaglandin (PG) E2 is
known to play an essential role. It has been proposed that, during
infections, PGE2 is produced in brain vasculature
in response to immune signals, is released into the brain parenchyma,
activates PGE receptors located on neurons, and then triggers the
neural circuitry for fever induction (Elmquist et al., 1997; Matsumura
et al., 1998; Yamagata et al., 2001). However, the
PGE2-triggered neural mechanism for fever induction is still unknown.
The preoptic area (POA) is the major site of action of E-series PGs in
the induction of fever (Feldberg and Saxena, 1971; Stitt, 1973;
Williams et al., 1977). Our immunohistochemical studies have shown that
the EP3 subtype of PGE receptor is somatodendritically localized on
neurons in the POA, especially in its subregions, medial preoptic area
(MPO) and median preoptic nucleus (MnPO) (Nakamura et al., 1999,
2000). PGE2 has been thought to exert suppressive
effects on functions of the cells expressing EP3 receptor (for review,
see Negishi et al., 1995). Among mice lacking each of the known PGE
receptor subtypes, only EP3 receptor-deficient mice failed to show a
febrile response to PGE2, interleukin-1 , or
endotoxin (Ushikubi et al., 1998). These observations have led us to
hypothesize that the EP3 receptor on POA neurons is the target of
PGE2 for its pyrogenic action and that the
suppression of POA neuron activity through this receptor activation
triggers the neural processes for fever induction.
The action of PGE2 in the POA is thought to
trigger the efferent mechanisms that control peripheral sympathetic
effectors, including brown adipose tissue (BAT), which is known to be
the major organ for thermogenesis during fever in rodents (for review, see Rothwell, 1992). Neural tract tracing and physiological studies have suggested that the sympathetic premotor neurons controlling BAT
are distributed in some ventral medullary regions (Bamshad et al.,
1999; Uno and Shibata, 2001). For understanding the fever-inducing neural system, it is important to identify the sympathetic premotor regions that receive the pyrogenic PGE2 signal
from the POA. In the present study, the neuronal groups excited by
central PGE2 administrations were investigated in
the ventral medullary regions by immunohistochemically detecting Fos,
the protein product of the immediately early gene c-fos
(Sagar et al., 1988), and PGE2-excited neurons
were distributed in the raphe pallidus nucleus (RPa), especially in its
rostral part (rRPa). Next, the projection from EP3 receptor-expressing
POA neurons to the rRPa was examined with anterograde and retrograde
neural tract tracing techniques. Furthermore, the suppression of rRPa
neuron activity by microinjecting muscimol, a
GABAA receptor agonist, was used to examine the
role of the rRPa in the transmission of the pyrogenic signal of
PGE2 from the POA to the sympathetic effectors
contributing to fever development, including BAT.
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MATERIALS AND METHODS |
Animals. One hundred and twelve male Wistar rats
(200-250 gm; SLC Japan, Hamamatsu, Japan) were used in the present
study. They were housed three or four to a cage with ad
libitum access to food and water; the room was kept at 26 ± 2°C with a standard 12 hr light/dark cycle. All experimental
procedures were approved by the Animal Care and Use Committee of the
Graduate School of Biostudies at Kyoto University.
Intracerebroventricular PGE2
stimulation. Rats were deeply anesthetized with sodium
pentobarbital (50 mg/kg, i.p.) and positioned in a stereotaxic
apparatus (Narishige, Tokyo, Japan) according to the brain atlas of
Paxinos and Watson (1998). A stainless steel cannula (outer diameter,
0.35 mm) and a 1 ml disposable syringe were connected with polyethylene
tubing, and they were filled with pyrogen-free 0.9% saline (Otsuka,
Tokyo, Japan). The cannula was inserted perpendicularly into the right
lateral ventricle (coordinates: 0.8 mm posterior to the bregma, 1.4 mm
lateral to the midline, and 4.0 mm ventral to the skull surface). After
accuracy of the cannula placement was checked with a flow of the saline into the ventricle by hydrostatic pressure, the polyethylene tubing was
cut and its opening end was sealed with heat. The animals were kept for
at least 1 week to recover. One day before the experiment, the cannula
was flushed with pyrogen-free 0.9% saline. On the day of the
experiment, the rats were anesthetized with urethane (1.3 gm/kg, i.p.;
Sigma, St. Louis, MO) between 10 and 11 A.M. and left on a
self-regulating heating pad (KN-474; Natume, Tokyo, Japan) to stabilize
the rectal temperature (Trec) at
37°C. The Trec was monitored with a
copper-constantan thermocouple inserted into the rectum through the
anus. After 4 hr, PGE2 (500 ng; Sigma) in 15 µl
of pyrogen-free 0.9% saline or only saline was injected into the
ventricle through the cannula. After 1 hr of
Trec monitoring, the animals were
immediately fixed transcardially and expression of Fos protein in the
brain was immunohistochemically detected as described below.
Intra-MPO PGE2 microinjection. A
silica capillary (inner diameter 75 µm, outer diameter 150 µm) was
connected to Teflon tubing, and they were filled with pyrogen-free
0.9% saline containing 0.5 mg/ml PGE2 and 0.8%
fluorescent microspheres with a diameter of 0.1 µm (F-8801; Molecular
Probes, Eugene, OR). A 10 µl syringe (Hamilton, Reno, NV) filled with
mineral oil was connected to the other end of the Teflon tubing.
Urethane-anesthetized rats were positioned in a stereotaxic apparatus
and left on a self-regulating heating pad to stabilize the
Trec at 37°C. After 4 hr, the
capillary was perpendicularly inserted into the MPO (coordinates: 0.0 mm to the bregma, 0.5-1.0 mm lateral to the midline, and 8.0-8.5 mm
ventral to the brain surface), and then 100 nl of the
PGE2 solution or the vehicle alone was slowly
(10-20 sec) injected through the capillary using an infusion pump
(Harvard Apparatus, South Natick, MA). The volume of injection was
visually confirmed by movement of the aqua-oil interface along the
Teflon tubing, which was graduated. After 1 hr of
Trec monitoring, the animals were
immediately fixed and subjected to immunohistochemical detection of Fos
protein as described below.
Muscimol microinjection. Urethane-anesthetized rats were
positioned in a stereotaxic apparatus. To monitor the temperature of
the interscapular BAT (TBAT), a
copper-constantan thermocouple was inserted between the interscapular
BAT pad and the underlying connective tissue. The animals were left on
a self-regulating heating pad to stabilize the
Trec at 37°C in a chamber
air-conditioned at 25-27°C. After 2 hr, muscimol (1 mM, 60 nl; Sigma), dissolved in pyrogen-free
0.9% saline containing fluorescent microspheres, or its vehicle alone
was microinjected into the ventral medulla as described above in the
intra-MPO microinjection. The coordinates for the ventral medulla were
1.3-3.3 mm posterior to the interaural line, 0.0-2.4 mm lateral to
the midline, and 8.5-9.6 mm ventral to the brain surface. Ten minutes
after the muscimol microinjection, intracerebroventricular injection of
PGE2 (500 ng in 15 µl pyrogen-free 0.9%
saline) by the method of Cao et al. (1999) or intra-MPO microinjection of PGE2 (50 ng; see above) was performed. After 2 hr of TBAT and Trec recording, the rats were killed
by decapitation. Their brains were frozen and coronally sectioned at a
thickness of 20 µm with a cryostat. After the sections were stained
with toluidine blue, the locations of the microinjections were
identified by detecting the fluorescent microspheres under an
epifluorescence microscope (Eclipse E600; Nikon, Tokyo, Japan) and
plotted on drawings from a brain atlas (Paxinos and Watson, 1998).
Sindbis virus and tracer injection. Rats were deeply
anesthetized with chloral hydrate (280 mg/kg, i.p.) and placed in a
stereotaxic apparatus. For anterograde tracing studies, we used a
replication-deficient recombinant Sindbis virus containing a gene
encoding enhanced green fluorescent protein (EGFP) tagged with the
N-terminal palmitoylation signal peptide of growth associated
protein-43 (palEGFP) (Moriyoshi et al., 1996, Tamamaki et al., 2000)
that is driven by a subgenomic promoter of Sindbis virus for expression
in mammalian cells (Furuta et al., 2001). The virus solution (0.1-0.5
µl, 2 × 1010 infectious unit/ml)
was pressure-injected into the POA through a glass micropipette (tip
inner diameter 10-15 µm) with the aid of a Picospritzer II (General
Valve, Fairfield, NJ). The coordinates for the POA were 0.05 mm
posterior to the bregma, 0.7 mm lateral to the midline, and 8.5 mm
ventral to the brain surface. For retrograde tracing studies, a 4%
solution of Fluoro-Gold (0.1-1.0 µl; Fluorochrome, Denver, CO),
dissolved in 0.9% saline, was pressure injected into the ventral
medulla (1.3-3.3 mm posterior to the interaural line, 0.0 mm lateral
to the midline, and 9.0-9.6 mm ventral to the brain surface) through a
glass micropipette with the aid of a Picospritzer II. Eighteen hours
after the virus injection or 3 d after the Fluoro-Gold injection,
each animal was reanesthetized and subjected to the immunohistochemical
analyses described below. For tracing studies, expressed palEGFP was
visualized by its own fluorescence or by immunohistochemical staining
with an anti-EGFP antibody, and Fluoro-Gold was detected by its own fluorescence.
Immunohistochemistry. The immunohistochemical procedures
followed our previous studies (Nakamura et al., 2000, 2001). Briefly, the rats treated as described above were fixed by transcardial perfusion with 4% paraformaldehyde. The brains were postfixed in the
fixative, saturated with a sucrose solution, and then cut into 20- or
40-µm-thick coronal sections on a cryostat. The sections were
consecutively collected into six bottles; six series of sections were
obtained from each rat. The sections were incubated overnight with one
of the following antibodies: anti-Fos rabbit serum (Ab-5; Oncogene,
Cambridge, MA), 1:20,000; anti-rat EP3 receptor rabbit antibody
(Nakamura et al., 1999, 2000), 1 µg/ml; anti-EGFP rabbit antibody
(Tamamaki et al., 2000), 0.1 µg/ml. After a rinse, the sections were
incubated for 1 hr with 10 µg/ml biotinylated donkey antibody to
rabbit IgG (Chemicon, Temecula, CA). The sections were rinsed again and
reacted for 1 hr with ABC-Elite (1:50; Vector). After a thorough wash
of the sections, the bound peroxidase was finally visualized by
incubation with 0.02% 3,3'-diaminobenzidine tetrahydrochloride (DAB)
(Dojindo, Kumamoto, Japan) and 0.001% hydrogen peroxide in 50 mM Tris-HCl, pH 7.6.
For double-immunoperoxidase staining of Fos and serotonin, the sections
were incubated overnight with the anti-Fos rabbit serum and an
anti-serotonin goat serum (1:5000; DiaSorin, Stillwater, MN). After the
sections were incubated with biotinylated donkey antibody to goat IgG
(Chemicon) and then with ABC-Elite, the peroxidase was reacted with the
DAB solution described above. In this manner, immunoreactivity for
serotonin was visualized as a brown reaction product of DAB. The bound
peroxidase and unreacted avidin and biotin in the sections were blocked
with 3% hydrogen peroxide and an avidin-biotin blocking kit (Vector),
respectively. After a thorough wash, the sections were incubated with
biotinylated donkey antibody to rabbit IgG and then with ABC-Elite. The
sections were incubated with 0.02% DAB, 0.0002% hydrogen peroxide,
and 0.5% ammonium nickel sulfate hexahydrate in 50 mM
Tris-HCl, pH 7.6, to visualize Fos immunoreactivity as a blue-black
reaction product. By omitting one of the primary antibodies, we
confirmed that there was no cross-reactivity between the reagents
involved in the two different immunoperoxidase staining steps.
The POA sections from the Sindbis virus- or Fluoro-Gold-injected brains
were subjected to immunofluorescence labeling of EP3 receptor as
described (Nakamura et al., 2001). After sequential incubations with
anti-EP3 receptor rabbit antibody and with biotinylated donkey antibody
to rabbit IgG, the sections were incubated with 1 µg/ml Alexa
594-conjugated streptavidin (Molecular Probes). The sections were
thoroughly washed and mounted onto gelatin-coated glass slides. For
double-fluorescence microscopy, an Axiophot epifluorescence microscope
(Zeiss, Oberkochen, Germany) was used with an appropriate filter set
for Fluoro-Gold (excitation, 360-370 nm; emission,  395 nm), EGFP
(excitation, 450-490 nm; emission, 515-565 nm), or Alexa 594 (excitation, 530-585 nm; emission, 615 nm).
For the study of cytoarchitecture, one of the rostrocaudal series of
the immunolabeled sections was counterstained with cresyl violet. The
cytoarchitecture and nomenclature of Paxinos and Watson (1998) were
adopted in most regions of the brain, and for the definition of MPO and
MnPO we referred to the rat brain atlas by Swanson (1992).
In situ hybridization. Nonradioactive in
situ hybridization was performed as described elsewhere (Esclapez
et al., 1993). The antisense and sense probes for the 67 kDa form of
rat glutamic acid decarboxylase (GAD67) were 619 nucleotides in length.
Hybridization using the sense probe did not show any signals. After
in situ hybridization, the sections were subjected to
immunoperoxidase labeling of EP3 receptor.
Data analysis. All data are presented as the means with the
SEM (±SEM). Statistical analysis was performed using the unpaired Student's t test (Instat 2.00 program; Graph Pad, San
Diego, CA), and a result was considered significant given a
p value of <0.05.
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RESULTS |
PGE2-induced Fos expression
To identify fever-mediating brain regions, we administered
PGE2 centrally to trigger fever in rats and
examined neuronal activation in the brain by immunohistochemically
detecting Fos. In this investigation, we especially focused on the
ventral medullary nuclei that had been proposed to contain the
sympathetic premotor neurons controlling interscapular BAT (Bamshad et
al., 1999; Uno and Shibata, 2001): RPa, raphe magnus nucleus (RMg),
raphe obscurus nucleus (ROb), lateral paragigantocellular nucleus
(LPG), inferior olivary complex (IO), and rostroventrolateral reticular
nucleus (RVL). Intracerebroventricular administration of
PGE2 caused a significant rise in
Trec (fever) (2.5 ± 0.2°C in
PGE2-injected rats, n = 3;
0.13 ± 0.2°C in saline-injected rats, n = 3;
p < 0.005) and strikingly increased the density of Fos-positive cells in the RPa, especially in its portion rostral to the
rostral end of the IO, compared with saline administration (Fig.
1a). Thus, we nomenclaturally
divided the RPa into two parts: rostral and caudal to the rostral end
of the IO. These are denoted by rostral part (rRPa) and caudal part
(cRPa) of the RPa, respectively. The increase in the density of
Fos-positive cells was the most prominent in the caudal one-third of
the rRPa (Fig. 1a, Interaural  2.30
mm), but not observed in the rRPa at the level of the rostral end
of the facial nucleus (Fig. 1a, Interaural
1.30 mm) or in the cRPa (Fig. 1a,
Interaural 3.30 mm). The dense distribution of
the Fos-positive cell group in the rRPa extended into the RMg (Fig.
1a, PGE2, Interaural
2.30 mm). These Fos-positive cells in
PGE2-treated rats were immunoreactive for NeuN, a
marker for neurons (data not shown). To verify these observations
statistically, we counted the numbers of Fos-positive cells in the
ventral medullary regions that might be involved in the sympathetic
control of BAT (Bamshad et al., 1999; Uno and Shibata, 2001).
PGE2-treated rats exhibited significantly greater
numbers of Fos-positive cells in the rRPa (4.4-fold) and RMg (2.0-fold)
compared with saline-treated controls, whereas Fos expression in the
two treatment groups did not differ statistically in the ROb, cRPa,
LPG, IO, or RVL (Fig. 1b). These data raised the possibility
that the rRPa contains the sympathetic premotor neurons that control
BAT functions and consequently fever development.
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Figure 1.
Central PGE2 stimulations induce Fos
expression in rRPa neurons. a, Distribution of
Fos-immunoreactive cells (dots) in the ventral medulla
after intracerebroventricular injection of saline or PGE2.
Fos-immunoreactive cells in a 20-µm-thick frontal section of the
corresponding rostrocaudal position were plotted on a drawing. Sections
set in a row were taken from the same rostrocaudal position, and their (Figure legend continued.) distances from the
interaural line are indicated based on the brain atlas of Paxinos and
Watson (1998). b, The numbers of Fos-positive cells in
ventral medullary regions after intracerebroventricular injection of
saline (white bars) or PGE2 (black
bars). The numbers were counted in every sixth
20-µm-thick frontal section throughout the medulla oblongata. Each
bar represents the mean ± SEM of three rats per
group. Asterisks indicate statistically significant
differences between PGE2- and saline-injected groups
(p < 0.05). c,
Double-immunoperoxidase staining of Fos (blue-black) and
serotonin (brown) in the rRPa (Interaural
2.30 mm) after intracerebroventricular
PGE2 injection. Arrows and
arrowheads indicate cells with serotonin and Fos
immunoreactivity, respectively. d, A representative view
of an intra-MPO microinjection site. The injection site was clearly
identified as a cluster of fluorescent beads (arrow) in
the section counterstained with toluidine blue. e, Fos
immunoreactivity in the rRPa (Interaural 2.30
mm) after intra-MPO microinjection of saline or
PGE2. 3V, Third ventricle;
DAO, dorsal accessory olivary nucleus;
MAO, medial accessory olivary nucleus;
ox, optic chiasm; PIO, principal inferior
olivary nucleus; py, pyramidal tract. Scale bars:
a, d, 500 µm; c, 100 µm; e, 50 µm.
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In addition, the above results raised a question as to whether the
Fos-positive neurons in the rRPa and RMg after the
PGE2 administration were serotonergic, because
these regions are known to be rich in serotonergic neurons. Thus, we
performed double-immunoperoxidase staining for Fos and serotonin. As
shown in Figure 1c, most of the rRPa cells with Fos-positive
nuclei seen after intracerebroventricular PGE2
injection did not exhibit serotonin immunoreactivity. This observation
was assured by a statistical analysis; the PGE2
administration significantly increased the numbers of Fos-positive
cells in nonserotonergic cell groups of both rRPa and RMg but not in
serotonergic cell groups (Table 1).
To examine whether PGE2 triggers the excitation
of the rRPa neurons by acting on the POA, we next investigated Fos
expression after microinjection of PGE2 directly
into the POA. In the POA, EP3 receptor-expressing neurons were reported
to be densely localized in the MPO (Nakamura et al., 1999, 2000), and
PGE2 microinjection into this subregion was shown
to effectively induce fever (Scammell et al., 1996). Thus, to trigger
the pyrogenic neural mechanism in the POA, we microinjected
PGE2 into the MPO (Fig. 1d). Intra-MPO PGE2 microinjection reliably caused fever
(Trec rise; 1.6 ± 0.4°C in
PGE2-microinjected rats, n = 3;
0.21 ± 0.1°C in saline-microinjected rats, n = 3; p < 0.005) and induced Fos expression in many rRPa neurons compared with saline microinjection (Fig. 1e). Most
of these Fos-positive neurons were nonserotonergic, and the
distribution of these neurons was similar to that seen after the
intracerebroventricular injections (data not shown). The results from
the Fos-detection studies suggest that a neural system triggered by the
PGE2 action in the POA excites the
nonserotonergic neurons distributed in and around the rRPa.
Projection from EP3 receptor-expressing POA neurons to
the rRPa
Our observations then prompted us to investigate the neural
connections mediating the transmission of PGE2
signal from the POA to the rRPa. To this end, the projection from EP3
receptor-expressing POA neurons to the rRPa was studied using neural
tract tracing techniques. Recently, Furuta et al. (2001) have developed
a highly sensitive anterograde neural tract tracing technique using a
recombinant Sindbis virus that labels the infected neurons in a Golgi
stain-like manner. This virus was based on a replication-defective
Sindbis virus and designed for the infected cells to express a
membrane-targeted fluorescent protein, palEGFP, which is EGFP tagged
with a palmitoylation site (Tamamaki et al., 2000). In the
first of the present tract tracing studies, we injected the virus into
the POA and examined immunoreactivity for palEGFP in the rRPa. In rats
injected with the virus unilaterally into the MPO, many cells
exhibiting fluorescence of EGFP formed a cluster within the MPO (Fig.
2a), and this cell cluster was located over the EP3 receptor-immunoreactive neuronal group
(Fig. 2b). There were EP3 receptor-immunoreactive neuronal cells infected with the virus (Fig.
2c,d, arrow). In these rats, a
significant number of EGFP-immunoreactive fibers and boutons were
observed in the caudal one-third of the rRPa (Fig. 2e) and also in the RMg ipsilateral to the site of the virus injection (data
not shown). However, EGFP immunoreactivity was not evident in more
caudal regions, including the ROb, cRPa, and IO. These observations
were obtained from three rats in which we successfully injected the
virus into the MPO. Similar projections were also observed when we used
a conventional anterograde tracer, Phaseolus vulgaris
leucoagglutinin (data not shown).
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Figure 2.
Projections from POA neurons to the rRPa.
a, Sindbis virus injection into the POA. Infected cells
exhibited EGFP fluorescence and formed a cluster (enclosed with a
broken line), and many neuronal fibers with fluorescence
extended from the cell cluster. b, The location of the
Sindbis virus injection. A section adjacent to the one shown in
a was immunostained for EP3 receptor. The location of
the cluster of the infected cells is indicated by a broken
line. The cell cluster was located over the EP3
receptor-immunoreactive neuronal cell group in the MPO
(arrows). c, d, Infection
of EP3 receptor-expressing POA neurons with the Sindbis virus. There
were POA neuronal cell bodies double labeled with EGFP fluorescence
(c) and EP3 receptor immunoreactivity
(d) (arrow). The photomicrographs
were taken at the same site under different conditions of excitation.
e, EGFP immunoreactivity in the caudal one-third of the
rRPa. The immunoreactivity was localized in fibers
(arrows) and boutons (arrowheads).
ac, Anterior commissure. Scale bars: a,
100 µm; b, 500 µm; c,
d, 10 µm; e, 20 µm.
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We further analyzed the presence of EP3 receptor on the POA neurons
projecting to the ventral medullary regions by using Fluoro-Gold, a
retrograde neural tract tracer. Injection of the tracer into the caudal
one-third of the rRPa and surrounding RMg (Fig.
3a) resulted in double
labeling with Fluoro-Gold fluorescence and EP3 receptor
immunoreactivity in POA neurons (Fig. 3b,
arrows). These double-labeled cells were concentrated in the
MPO rather than in the MnPO (Fig. 3c). EP3 receptor
immunoreactivity was found in 43.0% of Fluoro-Gold-labeled cells in
the MPO, but in only 6.5% in the MnPO (counted within the EP3
receptor-immunoreactive region in every sixth 20-µm-thick
frontal section). EP3 receptor immunoreactivity was distributed also in
the dorsal part of the MnPO (dorsal to the anterior commissure) and in
the parastrial nucleus (Nakamura et al., 2000), but we scarcely found
Fluoro-Gold-labeled cells in these regions. We successfully performed
similar injections into three rats with the tracer and found no
significant differences in the observations between the animals. Using
the same procedure, we found that Fluoro-Gold injections centered on
the rostral one-third of the rRPa or on the cRPa showed no
double-labeled cells in the POA (data not shown). Similar results were
also obtained using another retrograde tracer, wheat germ agglutinin
(data not shown). The neural tract tracing studies demonstrate that a
population of EP3 receptor-expressing POA neurons project directly to
the caudal portion of the rRPa and its surrounding RMg.
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Figure 3.
EP3 receptor-expressing POA neurons
directly project to the rRPa. a, Fluoro-Gold
injection centered on the caudal one-third of the rRPa
(arrow). b, POA neuronal cell bodies
double labeled with Fluoro-Gold fluorescence and EP3 receptor
immunoreactivity (arrows). The photomicrographs were
taken at the same site under different conditions of excitation.
c, Distributions of POA neurons labeled with Fluoro-Gold
(open circles) and with both Fluoro-Gold and EP3
receptor immunoreactivity (filled circles). All
Fluoro-Gold-labeled cells distributed in the shown regions were drawn.
The distribution area of EP3 receptor-immunoreactive cells is colored
gray. Scale bars: a, c,
500 µm; b, 50 µm.
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Muscimol microinjection into the rRPa blocks
PGE2-induced fever and BAT thermogenesis
Our present results suggest that PGE2
excites rRPa neurons probably by acting on the EP3 receptor on POA
neurons, which hypothetically will lead to the activation of
sympathetic pathways projecting to the effectors contributing to fever
development, including BAT. We tested this functional relationship by
examining the effects of continuous inhibition of rRPa neurons on fever
and BAT thermogenesis evoked by intracerebroventricular or intra-MPO
PGE2 stimulation.
Intracerebroventricular PGE2 injection induced a
rise in TBAT of >2.0°C, peaking at
20-25 min after the injection. Trec,
the core temperature, started to increase 1-2 min after the
TBAT rise, and its peak was lower than
that of TBAT. The characteristics of
these temperature changes are consistent with the fact that heat is
produced in effectors including BAT during fever and then transferred
to the rest of the body. To continuously suppress neuronal activity, we
microinjected muscimol into the caudal one-third of the rRPa (Fig.
4c,d,
Interaural 2.30 mm). The muscimol pretreatment manifestly blocked the rise in both
TBAT and
Trec induced by
intracerebroventricular PGE2 administration (Fig.
4a,b). No TBAT
increase of >0.5°C was observed in the rats microinjected with
muscimol into the caudal one-third of the rRPa. In contrast, rats
microinjected with saline into the caudal one-third of the rRPa (Fig.
4d, open circles) showed
PGE2-induced
TBAT and
Trec rises to the level observed in
untreated rats (Fig. 4a,b).
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|
Figure 4.
Muscimol microinjection into the rRPa blocks fever
and BAT thermogenesis stimulated by intracerebroventricular
administration of PGE2. a, b,
Changes in TBAT (a)
and Trec (b) after
intracerebroventricular PGE2 injection in rats
microinjected with muscimol or saline into the caudal one-third of the
rRPa. The sites of muscimol and saline microinjections are shown in
d (Interaural 2.30 mm).
Each value represents the mean ± SEM of three rats per group. The
changes in TBAT and
Trec were significantly different between
muscimol- and saline-pretreated (Figure legend
continues.) (Figure legend continued.) groups at least
during the time period denoted by bars with
asterisks (p < 0.05). The
muscimol microinjections for showing in a and
b were selected from the ones shown in d
using anatomical criteria: the three microinjections closest to the
midline in the rRPa. The data shown in a and
b are from the same animals. c, A
representative view of muscimol microinjection. The injection site is
clearly identified as a cluster of fluorescent beads
(arrow) in the section counterstained with toluidine
blue. d, Composite drawing of the effect of muscimol or
saline microinjections into ventral medullary regions on BAT
thermogenesis stimulated by intracerebroventricular PGE2
injection. Each symbol represents the injection site and
corresponding change in TBAT 30 min after
PGE2 administration. The symbols located
outside the brain parenchyma indicate the cases of injections with
penetration of the capillary tip. Note the correlation with the
distribution of Fos-positive cells in the brain of
PGE2-administered rats shown in Figure 1a.
7, Facial nucleus; 7n, descending root of the
facial nerve; Am, ambiguus nucleus; g7,
genu of the facial nerve; Gi , alpha part of the
gigantocellular reticular nucleus; Giv, ventral part of
the gigantocellular reticular nucleus; Pr, prepositus
nucleus; Sol, nucleus of the solitary tract. Scale bar,
500 µm.
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|
To map the sites at which muscimol microinjection inhibited the
PGE2-stimulated BAT thermogenesis, we
microinjected muscimol into various regions of the ventral medulla,
examined the TBAT rises induced by
intracerebroventricular PGE2
injections, and graded the TBAT rises
as follows:  0.5°C, full inhibition; 0.5-2.0°C, partial
inhibition; 2.0°C, no inhibition. As shown in Figure 4d,
full inhibition (filled circles) was observed only
after muscimol was microinjected into the caudal one-third
of the rRPa. Muscimol microinjections into the regions
neighboring the most effective site, such as the middle one-third of
the rRPa, the caudal portions of the RMg, and the alpha part of
the gigantocellular reticular nucleus, only partially inhibited the BAT
thermogenesis (triangles). No inhibition
(crosses) was observed when muscimol microinjections were
made into the facial nucleus, ROb or the rostral one-third of the rRPa,
cRPa, IO, LPG, or RVL.
We further examined the blocking effect of the continuous inhibition of
rRPa neurons on fever and BAT thermogenesis caused by direct
PGE2 application into the MPO.
PGE2 microinjection into the MPO of untreated
rats increased TBAT by 2.0-3.0°C
and Trec by 1.5-2.0°C. Muscimol
microinjection into the caudal one-third of the rRPa (Fig.
5c, Interaural
2.30 mm) strongly inhibited the
TBAT and
Trec rises induced by intra-MPO
PGE2 microinjection (Fig.
5a,b); no TBAT
increase of >0.7°C was observed. In rats microinjected with muscimol
into the cRPa, IO, or RVL (Fig. 5c, Interaural
3.30 mm) or with saline into the caudal one-third of the
rRPa (Figs. 5a-c, Interaural
2.30 mm), intra-MPO PGE2 microinjection induced TBAT and
Trec rises to the level observed in
untreated rats. These results suggest that the rRPa mediates the
transmission of PGE2 signal from the POA to
fever-producing sympathetic effectors.
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[in a new window]
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Figure 5.
Fever and BAT thermogenesis induced by intra-MPO
microinjection of PGE2 are blocked by muscimol
microinjection into the rRPa. a, b,
Changes in TBAT (a)
and Trec (b) after
intra-MPO PGE2 microinjection in rats microinjected with
muscimol or saline into the caudal one-third of the rRPa. The sites of
muscimol and saline microinjections are shown in c
(Interaural 2.30 mm). Each value
represents the mean ± SEM of three rats per group. The changes in
TBAT and Trec
were significantly different between muscimol- and saline-pretreated
groups at least during the time period denoted by bars
with asterisks (p < 0.05).
The data shown in a and b are from the
same animals. c, Composite drawing of the effect of
muscimol or saline microinjections into ventral medullary regions on
BAT thermogenesis stimulated by intra-MPO PGE2
microinjection. Each symbol represents the site of
muscimol microinjection (filled circles and
crosses) or of saline microinjection (open
circles) and corresponding change in
TBAT 40 min after PGE2
microinjection: 0.7°C (filled circles);
2.0°C (crosses and open
circles).
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Expression of a marker for GABAergic neurons in EP3
receptor-expressing POA neurons
It has been documented that the EP3 receptor acts as a suppressive
receptor by coupling with inhibitory GTP-binding proteins (Negishi et
al., 1995). Therefore, our results appeared to mean that
PGE2-induced suppression of EP3
receptor-expressing POA neurons leads to the excitation of the rRPa
neurons. This raised the possibility of tonic inhibition of the rRPa
neurons by EP3 receptor-expressing POA neurons under
PGE2-free conditions. In addition, we showed that
GABA receptor-mediated inhibition of rRPa neurons blocked the
transmission of pyrogenic PGE2 signal from the
POA. Taken together, these lines of knowledge led us to hypothesize
that EP3 receptor-expressing POA neurons are GABAergic and directly regulate the activity of the rRPa neurons. To test this hypothesis, we
examined the expression of mRNA for GAD67, a marker for GABAergic neurons, in EP3 receptor-expressing POA neurons. By a combination of
immunoperoxidase staining for EP3 receptor and in situ
hybridization for GAD67, we found that 86.3% of EP3
receptor-immunoreactive POA neurons exhibited signals for GAD67 mRNA
(Fig. 6a,
arrows). This observation indicates that a large
population of EP3 receptor-expressing POA neurons are GABAergic,
supporting our hypothesis.
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|
Figure 6.
A population of EP3 receptor-expressing POA
neurons are GABAergic. a, Double labeling with
EP3 receptor immunoreactivity (brown) and GAD67 mRNA
hybridization (blue) in the POA. Arrows
indicate EP3 receptor immunoreactive neurons exhibiting signals for
GAD67 mRNA. Filled and open arrowheads
indicate neurons single labeled with GAD67 mRNA hybridization and EP3
receptor immunoreactivity, respectively. b, Our current
hypothesis on the neural pathway mediating PGE2-induced
fever. See Discussion for details. Blue,
red, and black circles denote cell bodies
of activated inhibitory neurons, activated excitatory neurons, and
suppressed neurons, respectively. IML, Intermediolateral
cell column. Scale bar, 30 µm.
|
|
| |
DISCUSSION |
The present study demonstrates, for the first time, that the rRPa
is essential for fever induction following central
PGE2 action. Muscimol microinjection into the
caudal one-third of the rRPa blocked fever and BAT thermogenesis caused
by central PGE2 administrations. Furthermore, the
PGE2 action prominently increased Fos expression
in a similar region of the rRPa. This
PGE2-induced increase in the number of
Fos-positive neurons within ventral medullary regions appeared to have
a good correlation with the blocking effect of the muscimol that was
microinjected into the regions. Thus, the GABAA
receptor agonist blocked the pyrogenic action of
PGE2, probably by suppressing the
PGE2-triggered excitation of the rRPa neurons. In
addition, it was reported that microinjection of bicuculline, a
GABAA receptor antagonist, into the rRPa caused a
rise in the sympathetic nerve activity to interscapular BAT (Morrison
et al., 1999). Taken together, it is likely that the rRPa neurons are
tonically inhibited by GABAergic inputs, and release of these neurons
from the tonic inhibition by a PGE2-triggered mechanism leads to the stimulation of the sympathetic system for fever development.
To trigger this fever-inducing mechanism, PGE2
appears to act on the POA, because the POA is almost the sole brain
region in which microinjections of PGE1, a
PGE2 analog, effectively evoked fever (Williams
et al., 1977). In the POA, especially in the MPO and MnPO, the EP3
subtype of PGE receptor was shown to be localized somatodendritically
on neurons (Nakamura et al., 1999, 2000). In addition, EP3
receptor-deficient mice failed to show a febrile response to
PGE2 (Ushikubi et al., 1998). Therefore, the
transmission of PGE2 signal from the EP3
receptor-expressing POA neurons is likely to be essential for fever induction.
How is the PGE2-evoked pyrogenic signal in the
POA transmitted to the rRPa neurons? Although abundant connections
between the POA and ventral medullary regions have been reported
(Murphy et al., 1999), the functional significance of these connections remains poorly understood. The present muscimol microinjection experiments indicate that descending transmission from the POA to the
rRPa is responsible for the PGE2-triggered
stimulation of the fever-producing sympathetic system. Our neural tract
tracing studies further revealed the direct projection from EP3
receptor-expressing POA neurons to the caudal portion of the rRPa,
suggesting a candidate component of the pyrogenic descending pathway.
In addition, the present double labeling for EP3 receptor and GAD67
mRNA showed that a major population of EP3 receptor-expressing POA
neurons are GABAergic. On the basis of these results, we propose a
possible mechanism of the pyrogenic transmission (Fig. 6b).
Under PGE2-free conditions, rRPa neurons are
tonically inhibited by inputs from EP3 receptor-expressing POA neurons,
which may be GABAergic (Fig. 6b, Normal);
PGE2, which is produced in brain vasculature
during infections (Elmquist et al., 1997; Matsumura et al., 1998;
Yamagata et al., 2001), suppresses the tonic firing of the POA neurons by activating the EP3 receptor, disinhibits the rRPa neurons, stimulates the sympathetic nervous system, and finally develops fever
(Fig. 6b, Infections).
In addition to the pyrogenic pathway that we propose here, there may be
other brain regions involved in fever induction. The paraventricular
hypothalamic nucleus (PVH) has been known as a major site of autonomic
control. It was reported that lesions of the PVH reduced febrile
responses to intracerebroventricular injection of
PGE2 or intraperitoneal administration of
endotoxin, although the lesions reduced the febrile responses only
partly and did not reduced fever induced by a high dose (50 ng) of
PGE2 (Horn et al., 1994). Thus, the PVH might
mediate in part the pyrogenic transmission from the POA to the rRPa.
Alternatively, the PVH might play an accessory role in the control of
the rRPa neurons independently of the descending pathway from the POA.
Another brain region, the ventromedial hypothalamic nucleus (VMH), has been associated with the sympathetic control of BAT (Perkins et al.,
1981; Imai-Matsumura et al., 1984; Niijima et al., 1984) and has been
proposed to mediate PGE2-stimulated BAT
thermogenesis (Amir and Schiavetto, 1990). However, a transneuronal
viral tract tracing study reported that there were little or no neural
connections between the VMH and interscapular BAT (Bamshad et al.,
1999). Furthermore, we found that the present Sindbis virus injections into the POA did not show significant EGFP-immunoreactive fibers or
boutons in the VMH (K. Nakamura, T. Kaneko, and M. Negishi, unpublished
observation). Therefore, it is unlikely that the VMH plays a
significant role in the pyrogenic transmission pathway from the POA.
RPa neurons project to the intermediolateral cell column (IML) of the
spinal cord (Loewy, 1981), which gives rise to outputs to control
various sympathetic effectors. Our Fos-detection studies suggest that
the rRPa neurons mediating the pyrogenic transmission are
nonserotonergic, and previous studies have shown that there is a
nonserotonergic population of spinally projecting neurons in the
medullary raphe nuclei (Bowker et al., 1981; Skagerberg and
Björklund, 1985). Thus, it is plausible that these
nonserotonergic rRPa neurons directly project to the IML and regulate
the sympathetic output to thermogenic effectors, including BAT (Fig.
6b).
Furthermore, the rRPa neurons receiving the descending transmission
from the POA may be involved in the regulation of a range of
functionally different sympathetic outflow systems in the IML. In the
rat, sympathetic control of tail skin blood flow is important for the
regulation of heat loss from the body, and during fever, reduction in
heat loss partly contributes to the rise in body temperature. An
anatomical study with viral tract tracer injections into the wall of
the tail artery showed transneuronal labeling of neurons in the RPa and
the POA (Smith et al., 1998). An electrophysiological study further
reported that glutamate injections close to midline medullary raphe
nuclei, including the RPa, activated tail sympathetic nerve activity
(Rathner and McAllen, 1999). These facts suggest the involvement of
POA-rRPa transmission in the sympathetic control of heat-loss
reduction during fever. In addition, central PGE2 administration is known to sympathetically increase blood pressure and
heart rate (Hoffman et al., 1986); it is possible that POA-rRPa transmission further mediates these cardiovascular responses to PGE2.
Our neural tract tracing studies have shown that most of the EP3
receptor-expressing POA neurons that likely control the rRPa are
distributed in the MPO, especially in its lateral part. A previous
study in which PGE2 was microinjected into
various POA subregions proposed that the ventromedial preoptic area
(VMPO) is a candidate region for the febrile action of
PGE2 (Scammell et al., 1996). However,
microinjections into the MPO or MnPO also effectively induced fever in
the same report (Scammell et al., 1996). Furthermore, a viral tract
tracing study suggested that sympathetic-related POA neurons were
distributed in the MPO and MnPO but scarcely in the VMPO (Westerhaus
and Loewy, 1999). Therefore, the lateral part of the MPO might be the
major site of action of PGE2 for fever induction
rather than the VMPO. In addition, the EP3 receptor-expressing POA
neuronal group may mediate induction of other inflammatory acute-phase
responses through as yet unidentified projections from these neurons,
because PGE2 produced during infections is
thought to induce various symptoms such as anorexia, headache, confusion, and malaise in addition to fever (Elmquist et al., 1997).
This gives us an idea that the EP3 receptor-expressing POA
neuronal group functions as an important "gate" through which immune signals are transmitted to diverse regions of the CNS and probably constitutes important neural pathways involved in the host
defense against diseases, of which fever is an important component.
| |
FOOTNOTES |
Received Nov. 28, 2001; revised Feb. 11, 2002; accepted March 18, 2002.
This work was supported by Grants-in-Aid for Scientific Research and
Special Coordination Funds for Promoting Science and Technology from
the Ministry of Education, Culture, Sports, Science and Technology of
Japan; by Grants-in-Aid for Scientific Research (B) of the Japan
Society for the Promotion of Science; and by a grant from the Naito
Foundation. K.N. is a Research Fellow of the Japan Society for the
Promotion of Science. We are grateful to Takahiro Furuta, Kouichi
Nakamura, and Dr. Nobuaki Tamamaki for providing Sindbis virus and
anti-EGFP antibody; to Ryohei Tomioka for technical support for
in situ hybridization; and to Akira Uesugi for
photographic support.
Correspondence should be addressed to Dr. Kazuhiro Nakamura, Department
of Morphological Brain Science, Graduate School of Medicine, Kyoto
University, Sakyo-ku, Kyoto 606-8501, Japan. E-mail: nkazuhir{at}pharm.kyoto-u.ac.jp.
| |
REFERENCES |
-
Amir S,
Schiavetto A
(1990)
Injection of prostaglandin E2 into the anterior hypothalamic preoptic area activates brown adipose tissue thermogenesis in the rat.
Brain Res
528:138-142[Web of Science][Medline].
-
Atkins E
(1960)
Pathogenesis of fever.
Physiol Rev
40:580-646[Free Full Text].
-
Atkins E,
Bodel P
(1972)
Fever.
N Engl J Med
286:27-34[Web of Science][Medline].
-
Bamshad M,
Song CK,
Bartness TJ
(1999)
CNS origins of the sympathetic nervous system outflow to brown adipose tissue.
Am J Physiol
276:R1569-R1578.
-
Bowker RM,
Westlund KN,
Coulter JD
(1981)
Origins of serotonergic projections to the spinal cord in rat: an immunocytochemical-retrograde transport study.
Brain Res
226:187-199[Web of Science][Medline].
-
Cao C,
Matsumura K,
Ozaki M,
Watanabe Y
(1999)
Lipopolysaccharide injected into the cerebral ventricle evokes fever through induction of cyclooxygenase-2 in brain endothelial cells.
J Neurosci
19:716-725[Abstract/Free Full Text].
-
Elmquist JK,
Scammell TE,
Saper CB
(1997)
Mechanisms of CNS response to systemic immune challenge: the febrile response.
Trends Neurosci
20:565-570[Web of Science][Medline].
-
Esclapez M,
Tillakaratne NJK,
Tobin AJ,
Houser CR
(1993)
Comparative localization of mRNAs encoding two forms of glutamic acid decarboxylase with nonradioactive in situ hybridization methods.
J Comp Neurol
331:339-362[Web of Science][Medline].
-
Feldberg W,
Saxena PN
(1971)
Further studies on prostaglandin E1 fever in cats.
J Physiol (Lond)
219:739-745[Abstract/Free Full Text].
-
Furuta T,
Tomioka R,
Taki K,
Nakamura K,
Tamamaki N,
Kaneko T
(2001)
In vivo transduction of central neurons using recombinant Sindbis virus: Golgi-like labeling of dendrites and axons with membrane-targeted fluorescent proteins.
J Histochem Cytochem
49:1497-1507[Abstract/Free Full Text].
-
Hoffman WE,
Albrecht RF,
Miletich DJ
(1986)
Effect of sympathetic blockade on central prostaglandin E2-induced hyperthermia.
Brain Res
367:73-76[Web of Science][Medline].
-
Horn T,
Wilkinson MF,
Landgraf R,
Pittman QJ
(1994)
Reduced febrile responses to pyrogens after lesions of the hypothalamic paraventricular nucleus.
Am J Physiol
267:R323-R328[Abstract/Free Full Text].
-
Imai-Matsumura K,
Matsumura K,
Nakayama T
(1984)
Involvement of ventromedial hypothalamus in brown adipose tissue thermogenesis induced by preoptic cooling in rats.
Jpn J Physiol
34:939-943[Web of Science][Medline].
-
Kluger MJ
(1991)
Fever: role of pyrogens and cryogens.
Physiol Rev
71:93-127[Abstract].
-
Loewy AD
(1981)
Raphe pallidus and raphe obscurus projections to the intermediolateral cell column in the rat.
Brain Res
222:129-133[Web of Science][Medline].
-
Matsumura K,
Cao C,
Ozaki M,
Morii H,
Nakadate K,
Watanabe Y
(1998)
Brain endothelial cells express cyclooxygenase-2 during lipopolysaccharide-induced fever: light and electron microscopic immunocytochemical studies.
J Neurosci
18:6279-6289[Abstract/Free Full Text].
-
Moriyoshi K,
Richards LJ,
Akazawa C,
O'Leary DDM,
Nakanishi S
(1996)
Labeling neural cells using adenoviral gene transfer of membrane-targeted GFP.
Neuron
16:255-260[Web of Science][Medline].
-
Morrison SF,
Sved AF,
Passerin AM
(1999)
GABA-mediated inhibition of raphe pallidus neurons regulates sympathetic outflow to brown adipose tissue.
Am J Physiol
276:R290-R297.
-
Murphy AZ,
Rizvi TA,
Ennis M,
Shipley MT
(1999)
The organization of preoptic-medullary circuits in the male rat: evidence for interconnectivity of neural structures involved in reproductive behavior, antinociception and cardiovascular regulation.
Neuroscience
91:1103-1116[Web of Science][Medline].
-
Nakamura K,
Kaneko T,
Yamashita Y,
Hasegawa H,
Katoh H,
Ichikawa A,
Negishi M
(1999)
Immunocytochemical localization of prostaglandin EP3 receptor in the rat hypothalamus.
Neurosci Lett
260:117-120[Web of Science][Medline].
-
Nakamura K,
Kaneko T,
Yamashita Y,
Hasegawa H,
Katoh H,
Negishi M
(2000)
Immunohistochemical localization of prostaglandin EP3 receptor in the rat nervous system.
J Comp Neurol
421:543-569[Web of Science][Medline].
-
Nakamura K,
Li Y-Q,
Kaneko T,
Katoh H,
Negishi M
(2001)
Prostaglandin EP3 receptor protein in serotonin and catecholamine cell groups: a double immunofluorescence study in the rat brain.
Neuroscience
103:763-775[Web of Science][Medline].
-
Negishi M,
Sugimoto Y,
Ichikawa A
(1995)
Molecular mechanisms of diverse actions of prostanoid receptors.
Biochim Biophys Acta
1259:109-120[Medline].
-
Niijima A,
Rohner-Jeanrenaud F,
Jeanrenaud B
(1984)
Role of ventromedial hypothalamus on sympathetic efferents of brown adipose tissue.
Am J Physiol
247:R650-R654.
-
Paxinos G,
Watson C
(1998)
In: The rat brain in stereotaxic coordinates, Ed 4. San Diego: Academic.
-
Perkins MN,
Rothwell NJ,
Stock MJ,
Stone TW
(1981)
Activation of brown adipose tissue thermogenesis by the ventromedial hypothalamus.
Nature
289:401-402[Medline].
-
Rathner JA,
McAllen RM
(1999)
Differential control of sympathetic drive to the rat tail artery and kidney by medullary premotor cell groups.
Brain Res
834:196-199[Web of Science][Medline].
-
Rothwell NJ
(1992)
Eicosanoids, thermogenesis and thermoregulation.
Prostaglandins Leukot Essent Fatty Acids
46:1-7[Web of Science][Medline].
-
Sagar SM,
Sharp FR,
Curran T
(1988)
Expression of c-fos protein in brain: metabolic mapping at the cellular level.
Science
240:1328-1331[Abstract/Free Full Text].
-
Scammell TE,
Elmquist JK,
Griffin JD,
Saper CB
(1996)
Ventromedial preoptic prostaglandin E2 activates fever-producing autonomic pathways.
J Neurosci
16:6246-6254[Abstract/Free Full Text].
-
Skagerberg G,
Björklund A
(1985)
Topographic principles in the spinal projections of serotonergic and non-serotonergic brainstem neurons in the rat.
Neuroscience
15:445-480[Web of Science][Medline].
-
Smith JE,
Jansen ASP,
Gilbey MP,
Loewy AD
(1998)
CNS cell groups projecting to sympathetic outflow of tail artery: neural circuits involved in heat loss in the rat.
Brain Res
786:153-164[Web of Science][Medline].
-
Stitt JT
(1973)
Prostaglandin E1 fever induced in rabbits.
J Physiol (Lond)
232:163-179[Abstract/Free Full Text].
-
Swanson LW
(1992)
In: Brain maps: structure of the rat brain. Amsterdam: Elsevier.
-
Tamamaki N,
Nakamura K,
Furuta T,
Asamoto K,
Kaneko T
(2000)
Neurons in Golgi-stain-like images revealed by GFP-adenovirus infection in vivo.
Neurosci Res
38:231-236[Web of Science][Medline].
-
Uno T,
Shibata M
(2001)
Role of inferior olive and thoracic IML neurons in nonshivering thermogenesis in rats.
Am J Physiol
280:R536-R546[Abstract/Free Full Text].
-
Ushikubi F,
Segi E,
Sugimoto Y,
Murata T,
Matsuoka T,
Kobayashi T,
Hizaki H,
Tuboi K,
Katsuyama M,
Ichikawa A,
Tanaka T,
Yoshida N,
Narumiya S
(1998)
Impaired febrile response in mice lacking the prostaglandin E receptor subtype EP3.
Nature
395:281-284[Medline].
-
Westerhaus MJ,
Loewy AD
(1999)
Sympathetic-related neurons in the preoptic region of the rat identified by viral transneuronal labeling.
J Comp Neurol
414:361-378[Web of Science][Medline].
-
Williams JW,
Rudy TA,
Yaksh TL,
Viswanathan CT
(1977)
An extensive exploration of the rat brain for sites mediating prostaglandin-induced hyperthermia.
Brain Res
120:251-262[Web of Science][Medline].
-
Yamagata K,
Matsumura K,
Inoue W,
Shiraki T,
Suzuki K,
Yasuda S,
Sugiura H,
Cao C,
Watanabe Y,
Kobayashi S
(2001)
Coexpression of microsomal-type prostaglandin E synthase with cyclooxygenase-2 in brain endothelial cells of rats during endotoxin-induced fever.
J Neurosci
21:2669-2677[Abstract/Free Full Text].
Copyright © 2002 Society for Neuroscience 0270-6474/02/22114600-11$05.00/0
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|
|
H. Tsuchiya, T. Oka, K. Nakamura, A. Ichikawa, C. B. Saper, and Y. Sugimoto
Prostaglandin E2 Attenuates Preoptic Expression of GABAA Receptors via EP3 Receptors
J. Biol. Chem.,
April 18, 2008;
283(16):
11064 - 11071.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
Y. Ootsuka, W. W. Blessing, A. A. Steiner, and A. A. Romanovsky
Fever response to intravenous prostaglandin E2 is mediated by the brain but does not require afferent vagal signaling
Am J Physiol Regulatory Integrative Comp Physiol,
April 1, 2008;
294(4):
R1294 - R1303.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
S. Matsumura, T. Shibakusa, T. Fujikawa, H. Yamada, K. Matsumura, K. Inoue, and T. Fushiki
Intracisternal administration of transforming growth factor- evokes fever through the induction of cyclooxygenase-2 in brain endothelial cells
Am J Physiol Regulatory Integrative Comp Physiol,
January 1, 2008;
294(1):
R266 - R275.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
J. A. DiMicco and D. V. Zaretsky
The dorsomedial hypothalamus: a new player in thermoregulation
Am J Physiol Regulatory Integrative Comp Physiol,
January 1, 2007;
292(1):
R47 - R63.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
K. Nakamura and S. F. Morrison
Central efferent pathways mediating skin cooling-evoked sympathetic thermogenesis in brown adipose tissue
Am J Physiol Regulatory Integrative Comp Physiol,
January 1, 2007;
292(1):
R127 - R136.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
J. S. Kroin, A. Buvanendran, D. E. Watts, C. Saha, and K. J. Tuman
Upregulation of cerebrospinal fluid and peripheral prostaglandin E2 in a rat postoperative pain model.
Anesth. Analg.,
August 1, 2006;
103(2):
334 - 43, table of contents.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
A. S. C. Fabricio, G. Tringali, G. Pozzoli, M. C. Melo, J. A. Vercesi, G. E. P. Souza, and P. Navarra
Interleukin-1 mediates endothelin-1-induced fever and prostaglandin production in the preoptic area of rats
Am J Physiol Regulatory Integrative Comp Physiol,
June 1, 2006;
290(6):
R1515 - R1523.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
M. W. Nason Jr and P. Mason
Medullary Raphe Neurons Facilitate Brown Adipose Tissue Activation
J. Neurosci.,
January 25, 2006;
26(4):
1190 - 1198.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
R. M. McAllen, M. Farrell, J. M. Johnson, D. Trevaks, L. Cole, M. J. McKinley, G. Jackson, D. A. Denton, and G. F. Egan
Human medullary responses to cooling and rewarming the skin: A functional MRI study
PNAS,
January 17, 2006;
103(3):
809 - 813.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
J. A. DiMicco and D. V. Zaretsky
The mysterious role of prostaglandin E2 in the medullary raphe: a hot topic or not?
Am J Physiol Regulatory Integrative Comp Physiol,
December 1, 2005;
289(6):
R1589 - R1591.
[Full Text]
[PDF]
|
|
|
|
|
|
|
M. Tanaka and R. M. McAllen
A subsidiary fever center in the medullary raphe?
Am J Physiol Regulatory Integrative Comp Physiol,
December 1, 2005;
289(6):
R1592 - R1598.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
S. Saha, L. Engstrom, L. Mackerlova, P.-J. Jakobsson, and A. Blomqvist
Impaired febrile responses to immune challenge in mice deficient in microsomal prostaglandin E synthase-1
Am J Physiol Regulatory Integrative Comp Physiol,
May 1, 2005;
288(5):
R1100 - R1107.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
Y. Ootsuka and W. W. Blessing
Activation of slowly conducting medullary raphe-spinal neurons, including serotonergic neurons, increases cutaneous sympathetic vasomotor discharge in rabbit
Am J Physiol Regulatory Integrative Comp Physiol,
April 1, 2005;
288(4):
R909 - R918.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
C.-S. Chiu, S. Brickley, K. Jensen, A. Southwell, S. Mckinney, S. Cull-Candy, I. Mody, and H. A. Lester
GABA Transporter Deficiency Causes Tremor, Ataxia, Nervousness, and Increased GABA-Induced Tonic Conductance in Cerebellum
J. Neurosci.,
March 23, 2005;
25(12):
3234 - 3245.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
A. S. C. Fabricio, F. H. Veiga, R. Cristofoletti, P. Navarra, and G. E. P. Souza
The effects of selective and nonselective cyclooxygenase inhibitors on endothelin-1-induced fever in rats
Am J Physiol Regulatory Integrative Comp Physiol,
March 1, 2005;
288(3):
R671 - R677.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
W.-H. Cao and S. F. Morrison
Brown adipose tissue thermogenesis contributes to fentanyl-evoked hyperthermia
Am J Physiol Regulatory Integrative Comp Physiol,
March 1, 2005;
288(3):
R723 - R732.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
M. W. Nason Jr. and P. Mason
Modulation of Sympathetic and Somatomotor Function by the Ventromedial Medulla
J Neurophysiol,
July 1, 2004;
92(1):
510 - 522.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
K. Nakamura, K. Matsumura, T. Hubschle, Y. Nakamura, H. Hioki, F. Fujiyama, Z. Boldogkoi, M. Konig, H.-J. Thiel, R. Gerstberger, et al.
Identification of Sympathetic Premotor Neurons in Medullary Raphe Regions Mediating Fever and Other Thermoregulatory Functions
J. Neurosci.,
June 9, 2004;
24(23):
5370 - 5380.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
S. F. Morrison
Activation of 5-HT1A receptors in raphe pallidus inhibits leptin-evoked increases in brown adipose tissue thermogenesis
Am J Physiol Regulatory Integrative Comp Physiol,
May 1, 2004;
286(5):
R832 - R837.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
S. F. Morrison
Central Pathways Controlling Brown Adipose Tissue Thermogenesis
Physiology,
April 1, 2004;
19(2):
67 - 74.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
C. J. Madden and S. F. Morrison
Excitatory amino acid receptors in the dorsomedial hypothalamus mediate prostaglandin-evoked thermogenesis in brown adipose tissue
Am J Physiol Regulatory Integrative Comp Physiol,
February 1, 2004;
286(2):
R320 - R325.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
B. CANNON and J. NEDERGAARD
Brown Adipose Tissue: Function and Physiological Significance
Physiol Rev,
January 1, 2004;
84(1):
277 - 359.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
M. Maruyama, M. Nishi, M. Konishi, Y. Takashige, K. Nagashima, T. Kiyohara, and K. Kanosue
Brain regions expressing Fos during thermoregulatory behavior in rats
Am J Physiol Regulatory Integrative Comp Physiol,
November 1, 2003;
285(5):
R1116 - R1123.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
A. A. Romanovsky, N. Sugimoto, C. T. Simons, and W. S. Hunter
The organum vasculosum laminae terminalis in immune-to-brain febrigenic signaling: a reappraisal of lesion experiments
Am J Physiol Regulatory Integrative Comp Physiol,
August 1, 2003;
285(2):
R420 - R428.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
D. V. Zaretsky, M. V. Zaretskaia, and J. A. DiMicco
Stimulation and blockade of GABAA receptors in the raphe pallidus: effects on body temperature, heart rate, and blood pressure in conscious rats
Am J Physiol Regulatory Integrative Comp Physiol,
July 1, 2003;
285(1):
R110 - R116.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
Z.-H. Zhang, S.-G. Wei, J. Francis, and R. B. Felder
Cardiovascular and renal sympathetic activation by blood-borne TNF-alpha in rat: the role of central prostaglandins
Am J Physiol Regulatory Integrative Comp Physiol,
April 1, 2003;
284(4):
R916 - R927.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
A. Mouihate, M-S. Clerget-Froidevaux, K. Nakamura, M. Negishi, J. L. Wallace, and Q. J. Pittman
Suppression of fever at near term is associated with reduced COX-2 protein expression in rat hypothalamus
Am J Physiol Regulatory Integrative Comp Physiol,
September 1, 2002;
283(3):
R800 - R805.
[Abstract]
[Full Text]
[PDF]
|
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TOP
ABSTRACT
INTRODUCTION
