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The Journal of Neuroscience, March 1, 2003, 23(5):1557
BRIEF COMMUNICATION
The Wake-Promoting Hypocretin-Orexin Neurons Are in an Intrinsic
State of Membrane Depolarization
Emmanuel
Eggermann1, *,
Laurence
Bayer1, *,
Mauro
Serafin1, *,
Benoît
Saint-Mleux1,
Laurent
Bernheim1,
Danièle
Machard1,
Barbara E.
Jones2, and
Michel
Mühlethaler1
1 Département de Physiologie, Centre
Médical Universitaire, 1211 Geneva 4, Switzerland, and
2 Department of Neurology and Neurosurgery, McGill
University, Montreal Neurological Institute, Montreal, Quebec, Canada
H3A 2B4
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ABSTRACT |
Wakefulness depends on the activity of hypocretin-orexin
neurons because their lesion results in narcolepsy. How these neurons maintain their activity to promote wakefulness is not known. Here, by
recording for the first time from hypocretin-orexin neurons and
comparing their properties with those of neurons expressing melanin-concentrating hormone, we show that hypocretin-orexin neurons
are in an intrinsic state of membrane depolarization that promotes
their spontaneous activity. We propose that wakefulness and associated
energy expenditure thus depend on that property, which allows the
hypocretin-orexin neurons to maintain a tonic excitatory influence on
the central arousal and peripheral sympathetic systems.
Key words:
arousal; melanin-concentrating hormone; MCH; rat; sleep; wakefulness
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Introduction |
Wakefulness has been shown to depend
on the newly identified hypocretin-orexin (Hcrt/Orx) neuropeptides (de
Lecea et al., 1998 ; Sakurai et al., 1998) by findings that alterations
in their precursor protein, their receptors, or the neurons that
produce them lead to the sleep disorder narcolepsy in both animals and humans (Chemelli et al., 1999; Lin et al., 1999; Peyron et al., 2000;
Thannickal et al., 2000). In normal individuals, Hcrt/Orx neurons, by
their activity, presumably provide a waking drive to the multiple
activating systems to which they project (Peyron et al., 1998),
including the central arousal and peripheral sympathetic systems. A
persistent drive on these targeted systems would underlie the dual role
of the Hcrt/Orx neurons in simultaneously promoting waking and energy
expenditure, functions that are compromised in narcolepsy and the
moderate obesity that follows their lesion (Hara et al., 2001). Without
recording from identified Hcrt/Orx neurons, the properties that allow
them to fulfill this unique role remain unknown (for review, see
Siegel, 1999; Kilduff and Peyron, 2000; Hungs and Mignot, 2001; Willie
et al., 2001). Indeed, whether these cells depend on inputs from other
systems or could be endowed with particular membrane properties for
their activity remains to be determined.
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Materials and Methods |
Electrophysiology. Coronal brain slices containing
numerous Hcrt/Orx neurons in the perifornical area of the hypothalamus were chosen according to the atlas of Peyron et al. (1998). In the same
area, but in smaller number, neurons containing melanin-concentrating hormone (MCH) are intermingled with Hcrt/Orx neurons. Before use, slices (300-µm-thick) obtained from young rats (15-28 d) were incubated at room temperature in artificial CSF (ACSF)
containing the following (in mM): 130 NaCl, 5 KCl, 1.25 KH2PO4, 1.3 MgSO4, 20 NaHCO3, 10 glucose, and 2.4 CaCl2 (bubbled with 95%
O2 and 5% CO2). For
sodium substitutions, we used the following (in
mM): 145 N-methyl-D-glucamine (NMDG) (or
choline), 5 KCl, 10 HEPES, 10 glucose, 1.3 MgSO4,
2.4 CaCl2, pH 7.4. Whole-cell recordings were obtained (Bayer et al., 2002) with patch electrodes (8-12 M )
containing the following (in mM): 126 KMeSO4, 4 KCl, 5 MgCl2, 10 HEPES, 8 phosphocreatine, 3 Na2ATP, 0.1 NaGTP,
and 0.1 BAPTA, pH 7.3. Access resistance was between 15 and 25 M.
Values for membrane potentials are uncompensated for junction
potentials [estimated junction potential,  9.6 mV; based on the
JpCalc software provided with the data acquisition system by Axon
Instruments (Foster City, CA)]. In some experiments,
BAPTA was raised to 20 mM
(KMeSO4 and lowered to 86 mM). To identify cells, 0.2% neurobiotin was
added to the intrapipette solution.
Immunohistochemistry. After recordings, slices were immersed
successively in ice-cold 3% paraformaldehyde for 2-12 hr and in 30%
sucrose for 24-48 hr. They were then stored at 80°C to be later
cut with a cryostat in 45-µm-thick sections. After two rinses with
Tris NaCl, pH 7.4, sections were submitted to staining for Hcrt/Orx and
MCH. First, sections were incubated 24 hr at room temperature with a
goat polyclonal IgG against Hcrt/Orx A (dilution at 1:200; Santa Cruz
Biotechnology, Santa Cruz, CA) and with a rabbit polyclonal IgG against
MCH (dilution at 1:200; gift from Prof. D. Fellmann, University of
Besançon, Besançon, France). Second, they were
rinsed (two times) with Tris NaCl and incubated for 3 hr at room
temperature in the presence of an anti-goat IgG-Cy3, an anti-rabbit
IgG-7-amino-4-methylcoumarin-3-acetic acid, and Cy2-conjugated
streptavidin (dilutions at 1:200 for all antibodies; Jackson
ImmunoResearch, West Grove, PA). Neurobiotin-filled neurons
appeared in green, Hcrt/Orx-positive cells in red, and MCH-positive
cells in blue. In a few occasions only Hcrt/Orx-injected neurons were
sought, in which case a similar protocol but without MCH antiserum was
used. Specificity of MCH staining has been checked in previous studies
(references in Brischoux et al., 2002). For Hcrt/Orx staining,
specificity was demonstrated by preabsorption of the antiserum (1:100)
with orexin A (20 µg/ml).
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Results |
Identification of Hcrt/Orx neurons
Hypothalamic neurons were recorded in rat brain slices using the
whole-cell technique. Under infrared video microscopy, large-sized ( 20 µm) neurons were selected in the perifornical area, which is
known to contain a large number of Hcrt/Orx neurons intermingled with a
smaller population of cells containing the MCH (Broberger et al.,
1998), a peptide thought to exert an action opposite to Hcrt/Orx on
energy metabolism (Qu et al., 1996; Shimada et al., 1998). One class of
cells immediately became of interest as potentially expressing Hcrt/Orx
on the basis of its clear preponderance, representing 49.7% of cells
recorded in rats aged 15-20 d (n = 82 of 165) and up
to 71.7% in those aged 25-28 d (n = 33 of 46). The
main characteristic of cells belonging to this class are illustrated in
Figure 1A-C. First,
when they were depolarized from the resting level, they responded by
tonic firing with little adaptation (Fig.
1A1). As they were challenged by
depolarizing current pulses delivered from a hyperpolarized level, a
low-threshold spike (LTS) was revealed (Fig.
1A2,
A3, arrows), followed by a slow
afterdepolarization (ADP) (Fig.
1A3, asterisk).
Together, the LTS and ADP, shown separately in Figure
1A3, represent the key features
that distinguish these cells from all neighboring cells. It is also
noteworthy that the LTS in these neurons was never crowned (at any
membrane potential) by a high-frequency burst of action potentials.
Second, in the presence of hyperpolarizing current pulses, all of these
cells showed a membrane rectification characterized by a sag (Fig.
1B, dot), which in other neurons has been
identified as a time- and voltage-dependent rectification resulting
from the presence of an Ih current.
Finally, most neurons (n = 59 of 82, or 72%) with the
above characteristics were spontaneously active (Fig. 1C), with a mean firing frequency of 3.17 ± 1.53 Hz (for those active, n = 59). As evidenced in the presence of tetrodotoxin
(TTX) (1.0 µM) (Fig. 1C), neurons of
this type had a rather depolarized resting membrane potential
(mean ± SEM, 45.6 ± 1.53 mV; n = 11; see
Materials and Methods). Triple immunohistochemical staining for
neurobiotin (Fig. 1D), Hcrt/Orx (Fig.
1E), and MCH (Fig. 1F) revealed
that all neurons (n = 11 of 11) of this type were
Hcrt/Orx positive. In contrast, none of them were MCH positive. Similar
results were obtained with dual immunohistochemical staining for
neurobiotin and Hcrt/Orx alone (n = 7 of 7; data not
shown). In those injected cells in which morphology could be properly
evaluated (n = 12), we found that two Hcrt/Orx neurons
appeared bipolar, whereas the remaining (10 of 12) were multipolar
(three main dendrites).
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Figure 1.
Characterization of neurons expressing
Hcrt/Orx or MCH. A1, Tonic firing in
response to a depolarizing current pulse delivered from the level of
resting potential (arrowhead).
A2,
A3, LTS (arrow)
and ADP (asterisk) triggered by a depolarizing current
pulse delivered from an hyperpolarized level. Additional
hyperpolarization eliminates the LTS and the ADP (bottom
trace in A3).
B, Superimposed responses to hyperpolarizing pulses
suggesting the presence of an Ih current
(dot). Note that only the trace with the
deepest hyperpolarization is shown in full. C, Tonic
firing at rest and its elimination by TTX (1.0 µM)
to determine resting potentials. D, F,
Immunohistochemical identification of an Hcrt/Orx neuron injected with
neurobiotin (arrowhead in D) and
expressing immunoreactivity for Hcrt/Orx
(E) but not for the MCH
(F). G1,
Firing with accommodation triggered by a depolarizing current pulse
delivered from the resting potential level.
G2,
G3, Absence of either LTS or ADP in
response to depolarizing pulses applied from more hyperpolarized
levels. H, Responses to hyperpolarizing current pulses
demonstrating the absence (dot) of any sag that could
have indicated the presence of an Ih
current. I, Absence of spontaneous firing in such
neurons and their mean resting potential. J,
L, Immunohistochemical identification of an MCH neuron
injected with neurobiotin (arrowhead in
J) and expressing immunoreactivity for MCH
(L) but not for Hcrt/Orx
(K). Membrane potentials are as follows
(arrowheads): 47 mV (A), 44 mV
(B), 48 mV (C), 61 mV
(G), and 61 mV (H,
I). Fx, Fornix.
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Identification of MCH neurons
In striking contrast to the Hcrt/Orx neurons, another group of
cells (17.58% in rats aged 15-20 d, n = 29 of 165;
and 13.04% in those aged 25-28 d, n = 6 of 46) was
identified that had completely different characteristics. The first
defining property of this group was the complete absence of a sag
during hyperpolarizing pulses delivered from rest (Fig.
1H), thus indicating the absence of an
Ih current. Second, neurons having the
above-described property never displayed an LTS or an ADP (Fig.
1G1-G3).
Finally, these cells also differed from Hcrt/Orx neurons by the level
of their resting membrane potential, which was much more hyperpolarized (mean ± SEM, 61.6 ± 0.86 mV; n = 29).
None of these neurons discharged spontaneously (Fig.
1I). Indeed, their membrane characteristics appeared
to render them silent, at least in the absence of synaptic activity. As
illustrated in Figure
1J-L, triple labeling
revealed that all (n = 8 of 8) of the
neurobiotin-stained cells (Fig. 1J) of this group
were Hcrt/Orx negative (Fig. 1K) but MCH positive (Fig. 1L). In those injected cells in which
morphology could be properly evaluated (n = 6), we
found that MCH neurons were all multipolar (three to four main
dendrites).
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Figure 2.
Properties of hypocretin-orexin neurons.
A, Persistence of the LTS and ADP in the presence of TTX
(1.0 µM) and cesium chloride (2 mM).
Inset illustrates elimination of the time- and
voltage-dependent sag by cesium chloride. B,
D, Elimination of the ADP but persistence of the LTS in
presence of NMDG (B), BAPTA (20 mM;
C), or FFA (100 µM; D).
Inset in D shows that further addition of
Ni (200 µM) eliminates the LTS.
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Properties of Hcrt/Orx neurons
Given the evident importance of activity in Hcrt/Orx neurons for
maintaining wakefulness and promoting energy expenditure (for review,
see Kilduff and Peyron, 2000; Hungs and Mignot, 2001; Siegel et al.,
2001; Willie et al., 2001), we proceeded to further investigate their
intrinsic properties. We began by examining the nature of the ADP by
using TTX, a specific blocker of voltage-dependent sodium channels.
Although TTX (1.0 µM) eliminated the action potentials, it failed (n = 11 of 11) to suppress either the ADP or
the LTS, as illustrated in Figure 2A. As also shown
in this figure, cesium chloride (2-3 mM), which
completely eliminated the time- and voltage-dependent sag
attributable to the Ih
(n = 7 of 7) (Fig. 2A,
inset), affected neither the LTS nor the ADP. We then
hypothesized that the ADP might reflect the presence of a nonselective
cation current (Bal and McCormick, 1993). To test this hypothesis, we
first substituted sodium chloride with NMDG in the perfusion solution
and indeed found that it completely eliminated (n = 2 of 2) the ADP (Fig. 2B) without affecting the LTS.
This result was confirmed (n = 3 of 3) by substituting
sodium chloride with choline chloride that again eliminated the ADP but
left the LTS unaltered (data not shown). We subsequently tested the
calcium dependence of this ADP by internally perfusing BAPTA (20 mM) into the neurons (Fig. 2C) and
again observed that the ADP was eliminated (n = 7 of 7) but the LTS persisted. These results suggest that the ADP uncovered in
Hcrt/Orx neurons must be attributable to the presence of a strong
calcium-activated nonselective cation current
(ICAN) (Bal and McCormick, 1993;
Partridge et al., 1994). To further test this possibility, we finally
applied flufenamate (FFA), an anti-inflammatory drug known to block
such currents (Partridge and Valenzuela, 2000). As illustrated in
Figure 2D, when added to TTX, FFA (100-200
µM) completely eliminated the ADP
(n = 6 of 6) but left the LTS unaffected. As evidenced
in the inset of Figure
2D, adding small doses of nickel (Ni) (100-200 µM) to FFA (in the
presence of TTX) completely eliminated the LTS (n = 2 of 2). The latter result suggests that the LTS must depend on the
presence of low-voltage-activated (LVA) calcium channels, which are
known to be sensitive to small doses of nickel. It is probable that, in
the experimental condition used to reveal the ADP, it is actually the
calcium entering through these LVA channels that activates the
ICAN. As evidence for this point, it
is noteworthy that small doses of nickel (100-200
µM), when applied in the presence of TTX but in
the absence of FFA, indeed completely eliminated both the LTS and the
ADP (n = 3 of 3; data not shown).
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Figure 3.
Persistence of the membrane depolarization and
spontaneous activity of hypocretin-orexin neurons in conditions of
synaptic blockade and their inhibition by GABA. A,
Persistence of the membrane depolarization in TTX (1.0 µM), ionotropic blockers (MK801 at 20 µM,
NBQX at 10 µM, and bicuculline at 10 µM),
and an ACSF with 0.1 mM Ca2+ and 10 mM Mg2+. B, Persistence
of the spontaneous activity in the presence of synaptic blockade
(right is an enlargement of the area identified by an
asterisk in the left). C,
Inhibition by a brief application of muscimol (5 sec at 100 µM). Membrane potentials are as follows
(arrowheads): 42 mV (A), 43 mV
(B), and 44 mV (C).
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The membrane depolarization of Hcrt/Orx neurons persists when
either synaptic transmission or Ih are
suppressed
Although, as demonstrated above, Hcrt/Orx neurons are equipped
with a set of intrinsic properties, all potentially conducive of a high
level of electrical activity, it remains possible that the
major determinant for their depolarized and active state is of synaptic origin. Given the presence of spontaneous synaptic potentials in these cells, we tackled that question first by blocking ionotropic receptors to glutamate
[(+)-5-methyl-10,11-dihydro-5H-dibenzo [a,d] cyclohepten-5,10-imine
maleate (MK801) (20 µM) and
2,3-dihydroxy-6-nitro-7-sulfonyl-benzo[f]quinoxaline (NBQX) (10 µM) to block NMDA and AMPA
receptors, respectively] and GABA (bicuculline at 10 µM to block GABAA
receptors) and show that such a condition had no effect on either their
resting membrane potential (Fig.
3A) (n = 3 of 3 in the presence of TTX) or their spontaneous activity
(n = 6 of 6; data not shown). As a second step, we
tested the effect of a more general condition of synaptic blockade (0.1 mM Ca2+ and 10 mM Mg2+) and found
again that it affected neither the resting potential (Fig.
3A) (n = 5 of 5 in the presence of TTX) nor
the spontaneous activity (n = 3 of 3) (Fig.
3B) of these cells.
In addition to showing that the persistent depolarization and activity
of Hcrt/Orx neurons are not of synaptic origin, the above results
indicate that voltage-dependent calcium currents are not implicated
either. Along this line, it is noteworthy that the
Ih current, which could have been
involved in the depolarization and activity of Hcrt/Orx neurons, also
plays no role. Indeed, cesium (3 mM), which was
shown to block the Ih, affected
neither the resting potential (n = 5 of 5; data not
shown) nor the activity (n = 3 of 3; data not shown) of
these neurons.
Inhibition of Hcrt/Orx neurons by GABA
Of final notice, Hcrt/Orx neurons were strongly inhibited (Fig.
3C) by the GABAA agonist muscimol,
briefly applied at 100 µM (n = 4 of 4). This effect persisted in the presence of either TTX or a high
Mg2+-low
Ca2+ solution (altogether
n = 3 of 3; data not shown).
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Discussion |
This study presents the first recordings of identified Hcrt/Orx
and MCH neurons. It shows that Hcrt/Orx neurons, in contrast to MCH
neurons, are in a depolarized state that promotes their activity. This
property of Hcrt/Orx neurons could contribute importantly to their
suggested role in maintaining wakefulness.
Our data show first that the depolarized and active state of Hcrt/Orx
neurons is not of synaptic origin because it persists in a condition in
which synaptic transmission is blocked. As a result, one is led to
propose that the depolarized and active state of Hcrt/Orx neurons is
intrinsic in nature. Among the intrinsic properties that might play a
role in directly promoting the spontaneous firing of Hcrt/Orx neurons
are the presumed Ih and LVA currents, which in other neurons have been implicated in rhythmic activity. Such
is not the case here, however, because blocking either of these
currents had no influence on the spontaneous firing of Hcrt/Orx neurons. The conditions in which these currents would become active is
not known, but one might speculate that they could support activity in
the face of hyperpolarizing synaptic inputs. Hcrt/Orx cells are also
endowed with a presumed ICAN (Bal and
McCormick, 1993; Partridge et al., 1994), revealed as an ADP after
activation of an LVA current when the cells are depolarized from an
hyperpolarized level. An ICAN that
would only depend on the previous activation of an LVA current cannot,
however, explain the spontaneous firing of Hcrt/Orx cells as recorded
here, because the activity of these cells persists when
voltage-dependent calcium currents are blocked.
In view of the above, it is reasonable to assume that the key factor in
promoting the spontaneous activity of Hcrt/Orx cells is an intrinsic
state of membrane depolarization that keeps them constantly near their
firing threshold. Our data suggest, however, that this state does not
depend on the presence of either sodium or calcium voltage-dependent
currents and that the Ih current is
not implicated. Given the importance of the presumed
ICAN in Hcrt/Orx neurons, one is led
to speculate that this current could play an important role in the
persistent membrane depolarization. In that case, the calcium needed
for activation of ICAN could originate
from channels other than the voltage-dependent calcium channels or from
intracellular stores. A clear-cut demonstration that an
ICAN contributes to the state of
membrane depolarization of Hcrt/Orx neurons cannot, however, be
achieved at present given the absence of selective antagonists of
calcium-activated cation currents.
The enduring activity that results from the properties of Hcrt/Orx
neurons would allow them to excite in a persistent manner their
multiple targets (Peyron et al., 1998) that include the major central
activating systems (Jones, 2000). Indeed, the Hcrt/Orx peptides have
been shown recently to exert a depolarizing and excitatory effect on
noradrenergic (Hagan et al., 1999; Horvath et al., 1999; Bourgin et
al., 2000; Brown et al., 2001), histaminergic (Bayer et al., 2001;
Eriksson et al., 2001), cholinergic (Methippara et al., 2000; Eggermann
et al., 2001; Xi et al., 2001; Burlet et al., 2002), and thalamic
intralaminar (Bayer et al., 2002) neurons. The autochthonous drive to
these activating systems could in fact derive from the Hcrt/Orx
neurons, as evidenced by the dramatic consequences during wakefulness
of their destruction seen in transgenic mice and human narcoleptics
(Nishino et al., 2000; Peyron et al., 2000; Thannickal et al., 2000;
Hara et al., 2001).
The intrinsic properties of the Hcrt/Orx neurons suggest that their
natural state is depolarized and active, by which they would promote
wakefulness, and that their inhibition would be necessary for allowing
sleep when, from c-Fos studies, they indeed appear to be less active
(Estabrooke et al., 2001). Here, not surprisingly, we were able to
verify that Hcrt/Orx neurons are indeed inhibited by GABA. GABAergic
neurons, located in the preoptic and basal forebrain areas, which
project to the posterior hypothalamus and become active during sleep,
could provide this inhibition (Sherin et al., 1998; Szymusiak et al.,
1998; Gallopin et al., 2000) (for review, see Jones, 2000; Kilduff and
Peyron, 2000; Hungs and Mignot, 2001; Saper et al., 2001).
With respect to the influence of Hcrt/Orx neurons on metabolism, the
findings that narcoleptic patients have an increased body-mass index
(Schuld et al., 2000) and that mice with selective destruction of
Hcrt/Orx neurons become moderately obese although hypophagic (Hara et
al., 2001) suggest that Hcrt/Orx neurons also stimulate energy
expenditure. One possible mechanism for this action could be the
stimulatory effect of the Hcrt/Orx peptides on the sympathetic nervous
system (Antunes et al., 2001) to which they project (Peyron et al.,
1998). Here again, the intrinsic properties of Hcrt/Orx neurons, by
favoring their depolarized and active state, could enable them to exert
a tonic influence on the preganglionic sympathetic neurons. It is
notable that MCH neurons, which also have widespread projections
throughout the CNS (Bittencourt et al., 1992), but have in contrast
been linked to energy conservation and decreased metabolic rate (Qu et
al., 1996; Shimada et al., 1998), are hyperpolarized and inactive in the resting state. As suggested by a number of studies, MCH neurons must depend for their activation, as occurring particularly in conditions of food deprivation, on various hunger-satiety-related signals arising from the periphery and/or hypothalamic centers involved
in the control of feeding behavior (for review, see Spiegelman and
Flier, 2001).
In conclusion, our results lead us to propose that wakefulness and
associated energy expenditure could depend on the intrinsic characteristics of Hcrt/Orx neurons, which, by maintaining them active,
allow them to maintain an excitatory influence on their targeted
central arousal and peripheral sympathetic systems.
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FOOTNOTES |
Received Nov. 4, 2002; revised Dec. 6, 2002; accepted Dec. 11, 2002.
*
E.E., L.B., and M.S. contributed equally to this work.
This study was supported by the following: grants from the Swiss Fonds
National, Novartis, OTT, and de Reuter and Schmidheiny Foundations (M.M. and M.S.); the Canadian Medical Research Council (B.E.J.); and a Roche fellowship (L.B.).
Correspondence should be addressed to Dr. M. Mühlethaler, Centre
Médical Universitaire, Département de Physiologie, 1 Rue Michel-Servet, 1211 Genève 4, Suisse. E-mail:
michel.muhlethaler{at}medecine.unige.ch.
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References |
-
Antunes VR,
Brailoiu GC,
Kwok EH,
Scruggs P,
Dun NJ
(2001)
Orexins/hypocretins excite rat sympathetic preganglionic neurons in vivo and in vitro.
Am J Physiol Regul Integr Comp Physiol
281:R1801-R1807[Abstract/Free Full Text].
-
Bal T,
McCormick DA
(1993)
Mechanisms of oscillatory activity in guinea-pig nucleus reticularis thalami in vitro: a mammalian pacemaker.
J Physiol (Lond)
468:669-691[Abstract/Free Full Text].
-
Bayer L,
Eggermann E,
Serafin M,
Saint-Mleux B,
Machard D,
Jones BE,
Mühlethaler M
(2001)
Orexins (hypocretins) directly excite tuberomammillary neurons.
Eur J Neurosci
14:1571-1575[Web of Science][Medline].
-
Bayer L,
Eggermann E,
Saint-Mleux B,
Machard D,
Jones BE,
Muhlethaler M,
Serafin M
(2002)
Selective action of orexin (hypocretin) on nonspecific thalamocortical projection neurons.
J Neurosci
22:7835-7839[Abstract/Free Full Text].
-
Bittencourt JC,
Presse F,
Arias C,
Peto C,
Vaughan J,
Nahon JL,
Vale W,
Sawchenko PE
(1992)
The melanin-concentrating hormone system of the rat brain: an immuno- and hybridization histochemical characterization.
J Comp Neurol
319:218-245[Web of Science][Medline].
-
Bourgin P,
Huitron-Resendiz S,
Spier AD,
Fabre V,
Morte B,
Criado JR,
Sutcliffe JG,
Henriksen SJ,
de Lecea L
(2000)
Hypocretin-1 modulates rapid eye movement sleep through activation of locus coeruleus neurons.
J Neurosci
20:7760-7765[Abstract/Free Full Text].
-
Brischoux F,
Cvetkovic V,
Griffond B,
Fellmann D,
Risold PY
(2002)
Time of genesis determines projection and Neurokinin-3 expression patterns of diencephalic neurons containing melanin-concentrating hormone.
Eur J Neurosci
16:1672-1680[Medline].
-
Broberger C,
de Lecea L,
Sutcliffe JG,
Hokfelt T
(1998)
Hypocretin/orexin- and melanin-concentrating hormone-expressing cells form distinct populations in the rodent lateral hypothalamus: relationship to the neuropeptide Y and agouti gene-related protein systems.
J Comp Neurol
402:460-474[Web of Science][Medline].
-
Brown RE,
Sergeeva O,
Eriksson KS,
Haas HL
(2001)
Orexin A excites serotonergic neurons in the dorsal raphe nucleus of the rat.
Neuropharmacology
40:457-459[Web of Science][Medline].
-
Burlet S,
Tyler CJ,
Leonard CS
(2002)
Direct and indirect excitation of laterodorsal tegmental neurons by hypocretin/orexin peptides: implications for wakefulness and narcolepsy.
J Neurosci
22:2862-2872[Abstract/Free Full Text].
-
Chemelli RM,
Willie JT,
Sinton CM,
Elmquist JK,
Scammell T,
Lee C,
Richardson JA,
Williams SC,
Xiong Y,
Kisanuki Y,
Fitch TE,
Nakazato M,
Hammer RE,
Saper CB,
Yanagisawa M
(1999)
Narcolepsy in orexin knockout mice: molecular genetics of sleep regulation.
Cell
98:437-451[Web of Science][Medline].
-
de Lecea L,
Kilduff TS,
Peyron C,
Gao X,
Foye PE,
Danielson PE,
Fukuhara C,
Battenberg EL,
Gautvik VT,
Bartlett FS,
Frankel WN,
van den Pol AN,
Bloom FE,
Gautvik KM,
Sutcliffe JG
(1998)
The hypocretins: hypothalamus-specific peptides with neuroexcitatory activity.
Proc Natl Acad Sci USA
95:322-327[Abstract/Free Full Text].
-
Eggermann E,
Serafin M,
Bayer L,
Machard D,
Saint-Mleux B,
Jones BE,
Mühlethaler M
(2001)
Orexins/hypocretins excite basal forebrain cholinergic neurones.
Neuroscience
108:177-181[Web of Science][Medline].
-
Eriksson KS,
Sergeeva O,
Brown RE,
Haas HL
(2001)
Orexin/hypocretin excites the histaminergic neurons of the tuberomammillary nucleus.
J Neurosci
21:9273-9279[Abstract/Free Full Text].
-
Estabrooke I,
McCarthy M,
Ko E,
Chou T,
Chemelli R,
Yanagisawa M,
Saper C,
Scammell T
(2001)
Fos expression in orexin neurons varies with behavioral states.
J Neurosci
21:1656-1662[Abstract/Free Full Text].
-
Gallopin T,
Fort P,
Eggermann E,
Cauli B,
Luppi PH,
Rossier J,
Audinat E,
Mühlethaler M,
Serafin M
(2000)
Identification of sleep-promoting neurons in vitro.
Nature
404:992-995[Medline].
-
Hagan JJ,
Leslie RA,
Patel S,
Evans ML,
Wattam TA,
Holmes S,
Benham CD,
Taylor SG,
Routledge C,
Hemmati P,
Munton RP,
Ashmeade TE,
Shah AS,
Hatcher JP,
Hatcher PD,
Jones DN,
Smith MI,
Piper DC,
Hunter AJ,
Porter RA,
Upton N
(1999)
Orexin A activates locus coeruleus cell firing and increases arousal in the rat.
Proc Natl Acad Sci USA
96:10911-10916[Abstract/Free Full Text].
-
Hara J,
Beuckmann CT,
Nambu T,
Willie JT,
Chemelli RM,
Sinton CM,
Sugiyama F,
Yagami K,
Goto K,
Yanagisawa M,
Sakurai T
(2001)
Genetic ablation of orexin neurons in mice results in narcolepsy, hypophagia, and obesity.
Neuron
30:345-354[Web of Science][Medline].
-
Horvath TL,
Peyron C,
Diano S,
Ivanov A,
Aston-Jones G,
Kilduff TS,
van den Pol AN
(1999)
Hypocretin (orexin) activation and synaptic innervation of the locus coeruleus noradrenergic system.
J Comp Neurol
415:145-159[Web of Science][Medline].
-
Hungs M,
Mignot E
(2001)
Hypocretin/orexin, sleep and narcolepsy.
BioEssays
23:397-408[Web of Science][Medline].
-
Jones BE
(2000)
Basic mechanisms of sleep-wake state.
In: Principles and practice of sleep medicine, Ed 3 (Kryger MH,
Roth T,
Dement WC,
eds), pp 134-154. Philadelphia: Saunders.
-
Kilduff TS,
Peyron C
(2000)
The hypocretin/orexin ligand-receptor system: implications for sleep and sleep disorders.
Trends Neurosci
23:359-365[Web of Science][Medline].
-
Lin L,
Faraco J,
Li R,
Kadotani H,
Rogers W,
Lin X,
Qiu X,
de Jong PJ,
Nishino S,
Mignot E
(1999)
The sleep disorder canine narcolepsy is caused by a mutation in the hypocretin (orexin) receptor 2 gene.
Cell
98:365-376[Web of Science][Medline].
-
Methippara MM,
Alam MN,
Szymusiak R,
McGinty D
(2000)
Effects of lateral preoptic area application of orexin-A on sleep-wakefulness.
NeuroReport
11:3423-3426[Web of Science][Medline].
-
Nishino S,
Ripley B,
Overeem S,
Lammers GJ,
Mignot E
(2000)
Hypocretin (orexin) deficiency in human narcolepsy.
Lancet
355:39-40[Web of Science][Medline].
-
Partridge LD,
Valenzuela CF
(2000)
Block of hippocampal CAN channels by flufenamate.
Brain Res
867:143-148[Web of Science][Medline].
-
Partridge LD,
Muller TH,
Swandulla D
(1994)
Calcium-activated non-selective channels in the nervous system.
Brain Res Brain Res Rev
19:319-325[Medline].
-
Peyron C,
Tighe DK,
van den Pol AN,
de Lecea L,
Heller HC,
Sutcliffe JG,
Kilduff TS
(1998)
Neurons containing hypocretin (orexin) project to multiple neuronal systems.
J Neurosci
18:9996-10015[Abstract/Free Full Text].
-
Peyron C,
Faraco J,
Rogers W,
Ripley B,
Overeem S,
Charnay Y,
Nevsimalova S,
Aldrich M,
Reynolds D,
Albin R,
Li R,
Hungs M,
Pedrazzoli M,
Padigaru M,
Kucherlapati M,
Fan J,
Maki R,
Lammers GJ,
Bouras C,
Kucherlapati R,
Nishino S,
Mignot E
(2000)
A mutation in a case of early onset narcolepsy and a generalized absence of hypocretin peptides in human narcoleptic brains.
Nat Med
6:991-997[Web of Science][Medline].
-
Qu D,
Ludwig DS,
Gammeltoft S,
Piper M,
Pelleymounter MA,
Cullen MJ,
Mathes WF,
Przypek R,
Kanarek R,
Maratos-Flier E
(1996)
A role for melanin-concentrating hormone in the central regulation of feeding behaviour.
Nature
380:243-247[Medline].
-
Sakurai T,
Amemiya A,
Ishii M,
Matsuzaki I,
Chemelli RM,
Tanaka H,
Williams SC,
Richardson JA,
Kozlowski GP,
Wilson S,
Arch JR,
Buckingham RE,
Haynes AC,
Carr SA,
Annan RS,
McNulty DE,
Liu WS,
Terrett JA,
Elshourbagy NA,
Bergsma DJ,
Yanagisawa M
(1998)
Orexins and orexin receptors: a family of hypothalamic neuropeptides and G protein-coupled receptors that regulate feeding behavior.
Cell
92:573-585[Web of Science][Medline].
-
Saper CB,
Chou TC,
Scammell TE
(2001)
The sleep switch: hypothalamic control of sleep and wakefulness.
Trends Neurosci
24:726-731[Web of Science][Medline].
-
Schuld A,
Hebebrand J,
Geller F,
Pollmacher T
(2000)
Increased body-mass index in patients with narcolepsy.
Lancet
355:1274-1275[Web of Science][Medline].
-
Sherin JE,
Elmquist JK,
Torrealba F,
Saper CB
(1998)
Innervation of histaminergic tuberomammillary neurons by GABAergic and galaninergic neurons in the ventrolateral preoptic nucleus of the rat.
J Neurosci
18:4705-4721[Abstract/Free Full Text].
-
Shimada M,
Tritos NA,
Lowell BB,
Flier JS,
Maratos-Flier E
(1998)
Mice lacking melanin-concentrating hormone are hypophagic and lean.
Nature
396:670-674[Medline].
-
Siegel JM
(1999)
Narcolepsy: a key role for hypocretins (orexins).
Cell
98:409-412[Web of Science][Medline].
-
Siegel JM,
Moore R,
Thannickal T,
Nienhuis R
(2001)
A brief history of hypocretin/orexin and narcolepsy.
Neuropsychopharmacology
25:S14-S20[Medline].
-
Spiegelman BM,
Flier JS
(2001)
Obesity and the regulation of energy balance.
Cell
104:531-543[Web of Science][Medline].
-
Szymusiak R,
Alam N,
Steininger TL,
McGinty D
(1998)
Sleep-waking discharge patterns of ventrolateral preoptic/anterior hypothalamic neurons in rats.
Brain Res
803:178-188[Web of Science][Medline].
-
Thannickal TC,
Moore RY,
Nienhuis R,
Ramanathan L,
Gulyani S,
Aldrich M,
Cornford M,
Siegel JM
(2000)
Reduced number of hypocretin neurons in human narcolepsy.
Neuron
27:469-474[Web of Science][Medline].
-
Willie JT,
Chemelli RM,
Sinton CM,
Yanagisawa M
(2001)
To eat or to sleep? Orexin in the regulation of feeding and wakefulness.
Annu Rev Neurosci
24:429-458[Web of Science][Medline].
-
Xi M,
Morales FR,
Chase MH
(2001)
Effects on sleep and wakefulness of the injection of hypocretin-1 (orexin-A) into the laterodorsal tegmental nucleus of the cat.
Brain Res
901:259-264[Web of Science][Medline].
Copyright © 2003 Society for Neuroscience 0270-6474/03/2351557-06$05.00/0
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|
|
|
|
|
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|
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|
TOP
ABSTRACT
Introduction
Compound via MeSH
