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The Journal of Neuroscience, March 1, 2003, 23(5):1580
BRIEF COMMUNICATION
Calcium-Dependent Exocytosis of Atrial Natriuretic Peptide from
Astrocytes
Mojca
Kr an3, *,
Matja
Stenovec2, *,
Marko
Kreft1, 2,
Tina
Pangr i 2,
Sonja
Grilc1,
Philip G.
Haydon4, and
Robert
Zorec1, 2
1 Laboratory of Neuroendocrinology-Molecular Cell
Physiology, Institute of Pathophysiology, Medical Faculty, University
of Ljubljana, 1000 Ljubljana, Slovenia, 2 Celica Biomedical
Sciences Center, 1000 Ljubljana, Slovenia, 3 Institute of
Pharmacology and Toxicology, Medical Faculty, University of Ljubljana,
Slovenia, and 4 Department of Neuroscience, University of
Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104
 |
ABSTRACT |
Astrocytes are non-neuronal cells in the CNS, which, like
neurons, are capable of releasing neuroactive molecules. However, the
mechanism of release is ill defined. In this study, we investigated the
mechanism of release of atrial natriuretic peptide (ANP) from cultured
cortical astrocytes by confocal microscopy. To study the discharge of
this hormone, we transfected astrocytes with a construct to express
pro-ANP fused with the emerald green fluorescent protein (ANP.emd). The
transfection of cells with ANP.emd resulted in fluorescent puncta in
the cytoplasm that represent secretory organelles. If ANP is released
by exocytosis, in which the vesicle fuses with the plasma membrane,
then the total intensity of the green fluorescing probe should
decrease, whereas the vesicle membrane is incorporated into the plasma
membrane. To monitor exocytosis, we labeled the membrane with the
fluorescent styryldye FM 4-64, a reporter of cumulative exocytosis. The
application of ionomycin to elevate cytoplasmic
[Ca2+] increased the fluorescence intensity of FM
4-64, whereas that of ANP.emd decreased. These effects were not
observed in the absence of extracellular Ca2+,
suggesting that ANP is released by regulated
Ca2+-dependent exocytosis from astrocytes.
Key words:
astrocytes; glia; ANP; exocytosis; FM 4-64; fusion
pore
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Introduction |
Astrocytes synthesize, store, and
release many neuroactive compounds, including neurotransmitters
(Parpura et al., 1994 ), neurotrophins, eicosanoids, and neuropeptides
(Martin, 1992). A particular neuropeptide, atrial natriuretic peptide
(ANP), has already been immunohistochemically identified not only in
myocytes but also in neurons (McKenzie et al., 1990) and astrocytes
(McKenzie, 1992) of canine and human cerebral cortex (McKenzie et al.,
1994) and cerebellum (McKenzie et al., 2001). Myocardial cells store ANP in the form of prohormone in clathrin-coated vesicles (Klein et
al., 1993) and release it by exocytosis when the prohormone is
converted to the active form. The brain ANP is stored in vesicles and
is released as a 24-25 amino acid peptide. In the peripheral plasma,
the 28 amino acid form of ANP predominates (Samson, 1987). Brain ANP
content is significantly increased in astrocytes after experimental
brain infarction (Nogami et al., 2001), suggesting that this putative
neurotransmitter regulates cerebral blood flow. ANP is also involved in
the control of salt appetite, because the destruction of ANP receptors
eliminates the inhibition of salt appetite caused by an NaCl load
(Blackburn et al., 1995).
The mechanism of ANP release from astrocytes has not yet been
determined. The release of atrial ANP from atrial myocytes was found to
be triggered after muscarinic and vasopressin receptor activation
(Sonnenberg and Veress, 1984) or after hemodynamic changes induced by
isoproterenol and carbachol (Garcia et al., 1986), whereas for
hypothalamic neurons, a depolarization-induced, Ca2+-dependent mechanism of ANP release
was determined (Tanaka and Inagami, 1986).
It is known that intracellular Ca2+ levels
regulate the release of classical neurotransmitters, such as glutamate
(Araque et al., 2000; Pasti et al., 2001) and aspartate. Astrocytes
also possess several components of secretory apparatus, such as
synaptobrevin II, cellubrevin, syntaxin (Parpura et al., 1995), and
SNAP-23 (synaptosome-associated protein of 23 kDa) (Hepp et al.,
1999); hence, ANP could be released via
Ca2+-dependent exocytosis. To study the
mechanism of ANP release from astrocytes, we transfected cells with a
construct to express pro-ANP fused with the emerald green
fluorescent protein (ANP.emd) (Han et al., 1999).
We show here that this construct labels discrete puncta in the
cytoplasm that likely represent secretory organelles. Furthermore, we
demonstrate that the application of ionomycin, in the presence, but not
the absence, of extracellular calcium, increases the fluorescence intensity of FM 4-64, a fluorescent reporter of cumulative
exocytosis, whereas the fluorescence intensity of ANP.emd-transfected
cells decreases, suggesting that ANP is released via
Ca2+-dependent exocytosis.
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Materials and Methods |
Astrocyte culture. Astrocyte cultures were
prepared from the cortex of neonatal rats (3 d old) and cultured as
described previously (Schwartz and Wilson, 1992). Cells were grown in
high glucose DMEM, containing 10% fetal bovine serum, 1 mM pyruvate, 2 mM
glutamine, and 25 µg/ml penicillin-streptomycin in 95% air-5%
CO2.Confluent cultures were shaken at 225 rpm overnight, and the medium was changed the next morning; this was
repeated for a total of three times. After the third overnight shaking,
the cells were trypinsized and cultured for 24 hr in 10 µM cytosine arabinoside. After reaching confluence again, the cells were subcultured onto 22-mm-diameter circular poly-L-lysine-coated coverslips.
Lipofection. The plasmid encoding atrial natriuretic factor
tagged with emerald green fluorescent protein, ANP.emd (a gift of Dr.
Ed Levitan, University of Pittsburgh, Pittsburgh, PA) (Han et al.,
1999), was introduced into the astrocytes by means of lipofection using
the standard reference protocol of Invitrogen (Carlsbad,
CA). DNA was mixed with 6 µl of Plus Reagent (Invitrogen), diluted in
100 µl of serum-free DMEM, and incubated for 15 min at room
temperature (RT). Lipofectamine (4 µl; Invitrogen) was diluted in 100 µl of serum-free DMEM. After incubation, both solutions were mixed
and incubated again for 15 min at RT. In the meantime, astrocytes were
washed once with serum-free DMEM and supplemented with 800 µl of
DMEM. The lipofection mixture (200 µl) was pipetted onto the cells
that were incubated for an additional 3 hr at 95% O2-5% CO2 at 37°C. Then
30 µl of Ultroser G (Invitrogen, Grand Island,
NY) was added; DMEM was exchanged on the next day.
Confocal microscopy. Astrocyte-loaded coverslips were
transferred into the recording chamber on a confocal microscope (model LSM 510; Zeiss, Jena, Germany) and supplied with 400 µl
of extracellular solution containing FM 4-64 (4 µM; Molecular Probes, Leiden, The Netherlands). Cumulative exocytosis was monitored by measuring the
intensity of FM 4-64 fluorescence (Betz et al., 1992; Smith and Betz,
1996; Kilic et al., 2001). To achieve this objective, cells were
maintained in 4 µM FM 4-64, which initially
stains total plasma membrane. When vesicles subsequently fuse with the plasma membrane, the fluorescence intensity increases as FM 4-64 gains
access to this newly exposed membrane. We report the FM 4-64 as a
percentage change of the initial fluorescence before stimulus. A
gravity-feed perfusion system (1-2 ml/min) was used to apply ionomycin
(10 µM) dissolved in extracellular solution containing FM 4-64. Fluorescent images were acquired by a
plan-apochromatic oil immersion objective (63×, 1.4 numerical
aperture) using 488 nm argon-ion laser excitation.
ANP.emd and FM 4-64 fluorescence were separated using 505-530 nm
bandpass and 580 nm long-pass emission filters, respectively.
Images were stored on an IBM-PC compatible computer
(Siemens, Nixdorf, Germany) and quantitatively analyzed
using LSM 510 software (Zeiss) and a software
subroutine written in MATLAB 5.3 (MathWorks, Natick, MA), using
background subtraction. The number of points (vesicles) was determined
using the Scion Image software (Scion,
Frederick MD) and assuming that a point consists of at least five
pixels, with a threshold of 25% of maximal fluorescence intensity.
Solutions. The extracellular solution contained the
following (in mM): 130 NaCl, 5 KCl, 8 CaCl2, 1 MgCl2, 10 D-glucose, and 10 HEPES, pH adjusted to 7.2 using
NaOH. DMEM contained the following (in
mM): 4 HEPES, 5 Tricine, 2 L-glutamine, 10% newborn calf serum, and 0.01%
bovine serum albumin. If not stated otherwise, all chemicals were
obtained from Sigma (Darmstadt, Germany) and were of the highest purity grade.
Statistics. Statistical differences between FM 4-64 and
ANP.emd fluorescence changes in Ca2+-free
and Ca2+-containing solution were tested
using the Student's t test.
| |
Results |
Cultured cells were identified as astrocytes with
immunocytochemical staining using antibodies against glial fibrillary
acidic protein (data not shown), a molecule expressed only in
differentiated astrocytes (Kennedy et al., 1980). The release of ANP
from a single cell was studied by transfecting cells with a construct
to express ANP.emd, which was shown previously to be targeted to
secretory vesicles (Han et al., 1999). Figure
1 shows that, in transfected rat
astrocytes, green fluorescence appears in puncta throughout the
cytoplasm. These puncta represent ANP-containing vesicles because
immunocytochemical studies using an antibody against ANP and
synaptobrevin II, a vesicle-associated protein, revealed colocalization of the green puncta with the signal from the ANP antibody and the
synaptobrevin II antibody (data not shown). If ANP is released from
astrocytes by regulated exocytosis, then the intensity of the green
fluorescing probe should decrease (Han et al., 1999). Indeed, the
stimulation of cells by the application of ionomycin to increase
cytosolic [Ca2+] resulted in an apparent
decline in the number of green fluorescing puncta. We binarized the
image shown in Figure 2 and counted the 381 puncta before and 203 puncta after the stimulus. The average intensity of pixels was similar: before ionomycin application, 60.0 ± 0.7 arbitrary units; after, 56.8 ± 0.8 arbitrary
units (means ± SE). We also monitored time-dependent
changes in the fluorescence intensity by selecting a region of interest
in the image of the whole cell. Immediately after the application of ionomycin, the average green fluorescence intensity increased transiently by ~1%, which is likely attributable to the
neutralization of the vesicular pH through the
open fusion pore (Barg et al., 2002) (see
Discussion). Figures 3 and 4 show that, 1 min after the addition of ionomycin, the average green fluorescence
intensity declined by ~5%. These results are consistent with the
view that the decline in ANP.emd fluorescence is attributable to
regulated exocytosis.
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Figure 1.
Confocal image of cultured cortical astrocyte
transfected with an ANP.emd construct. Green fluorescent puncta
are individual secretory granules that store ANP.emd
(top). The same astrocyte is also observed under
differential interference contrast optics (bottom).
Scale bar, 2 µm.
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Figure 2.
Ionomycin causes exocytotic release of ANP.emd.
Confocal images of double-labeled astrocyte before
(left; 0 sec) and 60 sec after (right)
bath application of ionomycin (10 µM) in the presence of
2 mM Ca2+ in the bath solution.
Top, ANP.emd fluorescence. Bottom, FM
4-64 stain. Note the decreased number of green fluorescent puncta and a
large increase in the surface membrane area indicated by the intense FM
4-64 fluorescence staining after 60 sec. Scale bars, 5 µm.
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Figure 3.
Ca2+-dependent release of ANP
from cultured astrocytes. Normalized FM 4-64 fluorescence increase
(left) and ANP.emd fluorescence decrease
(right) obtained in a single astrocyte after the
application of 10 µM ionomycin in
Ca2+-free (top) and
Ca2+-containing (2 mM) extracellular
solution (bottom). The inset shows the
overlay of fluorescence changes obtained with ANP.emd
(filled symbols) and FM 4-64 (open
symbols), showing no delay in the onset of ionomycin-induced
fluorescence changes.
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Figure 4.
Mean relative change of FM 4-64 (left) and ANP.emd (right) fluorescence
obtained in different cells stimulated with 10 µM
ionomycin in extracellular solution containing 2 mM
Ca2+ (n = 7) and
Ca2+-free extracellular solution
(n = 5). Asterisks indicate a
statistically significant difference in the change in FM 4-64 and
ANP.emd fluorescence change in the presence or absence of extracellular
Ca2+ (FM 4-64, p = 0.0018;
ANP.emd, p = 0.036; t test).
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To test this hypothesis further, we monitored cumulative exocytosis by
using the FM 4-64 styryl fluorescent probe, which stains membranes
(Betz et al., 1992; Smith and Betz, 1996; Kilic et al., 2001). If the
ionomycin-induced decline in green fluorescence intensity is
attributable to regulated exocytosis, this should be associated with
the incorporation of the new vesicle membrane into the plasma membrane
(Smith and Betz, 1996); therefore, the intensity of FM 4-64 fluorescence should increase. In the presence of extracellular
Ca2+, the FM 4-64 fluorescence intensity
increased by ~30% 1 min after ionomycin application (Figs. 3, 4).
The comparison of the latencies of the two fluorescence traces recorded
in a single cell revealed no delay in the onset of the FM 4-64 fluorescence intensity increase and the change in green fluorescence
intensity (Fig. 3, inset). Both the ionomycin-induced
decline in the green fluorescence intensity and the ionomycin-induced
increase in the red fluorescence intensity are consistent with an
ionomycin-induced increased rate of exocytosis.
Regulated exocytosis requires a stimulus that results in an increase in
cytoplasmic Ca2+ concentration (Burgoyne
and Morgan, 1995; Calakos and Scheller, 1996). The application of the
calcium ionophore ionomycin (10 µM), which induces an
increase in cytosolic [Ca2+] in these
cells (data not shown), induced changes in probe fluorescence intensity
only in the presence of extracellular Ca2+
(Figs. 3, 4), which indicates that the release of ANP is mediated by
regulated, Ca2+-dependent exocytosis.
| |
Discussion |
Although a large number of substances are reported to be secreted
from astrocytes (Martin 1992, Parpura et al., 1994), there has been
considerable debate about the underlying mechanisms. For example, in
the case of the transmitter glutamate, the reversal of glutamate
transporters, anion transporter-dependent mechanisms, and
calcium-dependent exocytosis have all been proposed (Attwell, 1994).
Although evidence is emerging to support the presence of an exocytotic
mechanism, the demonstration of regulated exocytosis in these glial
cells has remained elusive. The aim of this study was to determine the
mechanism of ANP release from cultured rat cortical astrocytes and to
thereby ask whether elevated internal calcium stimulates exocytosis in
these non-neuronal cells. To this end, confocal microscopy was used. To
monitor the release of the neuropeptide, we transfected cells with a
construct to express ANP.emd (Han et al., 1999). In our successfully
transfected cells, fluorescence appeared as discrete puncta.
Calcium-dependent exocytosis
Consistent with the presence of a regulated exocytosis pathway,
the addition of the Ca2+ ionophore
ionomycin stimulated a reduction in the average fluorescent intensity of the cell that resulted from a reduction in the number of
ANP.emd puncta within the astrocyte. Because the omission of Ca2+ from the bathing medium prevented the
ionophore-induced release of ANP.emd, these data are consistent with
the Ca2+-dependent exocyotsis of peptide
from astrocytes.
To provide an alternative approach to study exocytosis, we asked
whether the ionophore-induced release of ANP caused a correlated increase in membrane surface area that would support the presence of
exocytotic release of this peptide. Using FM 4-64 to monitor cumulative
exocytosis (Betz et al., 1992; Smith and Betz, 1996; Kilic et al.,
2001), we found a Ca2+-dependent increase
in total FM 4-64 fluorescence intensity.
Fusion pore dilation
When the kinetics of cumulative exocytosis (FM 4-64) are
superimposed on the fluorescence of ANP.emd, no delay was observed between the stimulus and the increase of FM 4-64 intensity.
Immediately after ionomycin application, the intensity of ANP.emd
transiently increased. This increase in intensity results from the pH
sensitivity of ANP.emd (Barg et al., 2002). Before the opening of the
fusion pore, vesicles are acidic, which reduces the intensity of emd fluorescence. Immediately after the stimulus, the initial opening of
the fusion pore allowed protons to leave the vesicle, which led to a
dequenching and thus to an increase in ANP.emd fluorescence (Barg et
al., 2002). It is likely that the diameter of this initial fusion pore
is sufficiently large to permeate not only protons but also the
low-molecular-weight dye FM 4-64. After the initial rise in green
fluorescence, the intensity of ANP.emd decreased, which we interpret as
being attributable to the ANP.emd release into the bathing saline.
Regardless of the details of the kinetics of these fluorescence
changes, when taken together, these data show that the application of
ionomycin to elevate astrocytic internal [Ca2+] stimulated the release of ANP.emd
through an exocytotic mechanism.
This clear demonstration of the regulated exocytotic release of ANP
from astrocytes has two important outcomes for our understanding of the
physiology of astrocytes. First, the demonstration of
Ca2+-regulated exocyotsis in these
non-neuronal cells indicates that, other chemical transmitters released
from these cells, such as glutamate, have the potential to be released
by an exocytotic mechanism. Second, the demonstration of
Ca2+-dependent ANP release from astrocytes
raises the hypothesis that synaptic activity might regulate cerebral
blood flow via the release of ANP from astrocytes. According to this
notion, synaptic activity, which is known to be able to induce
Ca2+ signaling in astrocytes, could cause
the release of endogenous ANP from astrocytes to regulate the cerebral
microvessels. In agreement with this possibility, ANP has been
demonstrated to be present in astrocytes, and it has been suggested
that it may regulate cerebral blood flow (McKenzie et al., 2001),
because this peptide is known to cause vasodilation (Kubo et al.,
1992).
In summary, these studies demonstrate that an increase in the
cytoplasmic [Ca2+] causes the exocytotic
release of ANP from astrocytes. The demonstrated release of ANP from
astrocytes by an exocytotic pathway suggests that astrocytes actively
regulate their local neuronal, synaptic, and endothelial environment by
the release of a variety of chemical transmitters.
| |
FOOTNOTES |
Received Sept. 12, 2002; revised Dec. 10, 2002; accepted Dec. 12, 2002.
*
M.K. and M.S. contributed equally to this work.
This work was supported by Ministry of Education, Sciences and
Sports of The Republic of Slovenia Grant P3 521 0381, European Community Grant QLG3-CT 2001-2004, and Fogarty International Research Collaboration Award Grant R03-TW01293. We thank Dr. Ed Levitan for the
generous donation of the ANP.emd construct.
Correspondence should be addressed to Robert Zorec, Laboratory of
Neuroendocrinology-Molecular Cell Physiology, Institute of
Pathophysiology, Medical School, University of Ljubljana, Zaloka 4, 1000 Ljubljana, Slovenia. E-mail: robert.zorec{at}mf.uni-lj.si.
| |
References |
-
Araque A,
Li N,
Doyle RT,
Haydon PG
(2000)
SNARE-protein-dependent glutamate release from astrocytes.
J Neurosci
20:666-673[Abstract/Free Full Text].
-
Attwell D
(1994)
Glia and neurons in dialogue.
Nature
369:707-708[Medline].
-
Barg S,
Olofsson CS,
Schriever-Aeln J,
Wendt A,
Gebre-Medhin S,
Renstrom E,
Rorsman P
(2002)
Delay between fusion pore opening and peptide release from large dense-core vesicles in neuroendocrine cells.
Neuron
33:287-299[Web of Science][Medline].
-
Betz WJ,
Mao F,
Smith CB
(1992)
Activity-dependent fluorescent staining and destaining of living vertebrate motor nerve terminals.
J Neurosci
12:363-375[Abstract].
-
Blackburn RE,
Samson WK,
Fulton RJ,
Stricker EM,
Verbalis JG
(1995)
Central oxytocin and ANP receptors mediate osmotic inhibition of salt appetite in rats.
Am J Physiol
269:R245-R251[Abstract/Free Full Text].
-
Burgoyne BD,
Morgan A
(1995)
Ca2+ and secretory dynamics.
Trends Neurosci
18:191-196[Web of Science][Medline].
-
Calakos N,
Scheller RH
(1996)
Synaptic vesicle biogenesis, docking, and fusion: molecular description.
Physiol Rev
76:1-29[Abstract/Free Full Text].
-
Garcia R,
Lacance D,
Thibault G,
Cantin M,
Gutkowska J
(1986)
Mechanisms of release of atrial natriuretic factor. II. Effect of chronic administration of
 - and  -adrenergic and cholinergic agonists on plasma and atrial ANF in the rat.
Biochem Biophys Res Commun
136:510-520[Medline]. -
Han W,
Ng YK,
Axelrod D,
Levitan ES
(1999)
Neuropeptide release by efficient recruitment of diffusing cytoplasmic secretory vesicles.
Proc Natl Acad Sci USA
96:14577-14582[Abstract/Free Full Text].
-
Hepp R,
Perraut M,
Chasserot-Golaz S,
Galli T,
Aunis D,
Langley K,
Grant NJ
(1999)
Cultured glial cells express the SNAP-25 analogue SNAP-23.
Glia
27:181-187[Web of Science][Medline].
-
Kennedy PG,
Lisak RP,
Raff MC
(1980)
Cell type-specific markers for human glial and neuronal cells in culture.
Lab Invest
43:342-351[Web of Science][Medline].
-
Kilic G,
Angelson JK,
Cochilla AJ,
Nussinovitch I,
Betz WJ
(2001)
Sustained stimulation of exocytosis triggers continuous membrane retrieval in rat pituitary somatotrophs.
J Physiol (Lond)
532:771-783[Abstract/Free Full Text].
-
Klein RM,
Kelley KB,
Merisko-Liversidge EM
(1993)
A Clathrin-coated vesicle-mediated pathway in atrial natriuretic peptide (ANP) secretion.
J Mol Cell Cardiol
25:437-452[Medline].
-
Kubo SH,
Atlas SA,
Laragh JH,
Cody RJ
(1992)
Maintenance of forearm vasodilator action of atrial natriuretic factor in congestive heart failure secondary to ischemic or idiopathic dilated cardiomyopathy.
Am J Cardiol
69:1306-1309[Medline].
-
Martin DL
(1992)
Synthesis and release of neuroactive substances by glia.
Glia
5:81-94[Web of Science][Medline].
-
McKenzie JC
(1992)
Atrial natriuretic peptide-like immunoreactivity in astrocytes of parenchyma and glia limitans of the canine brain.
J Histochem Cytochem
40:1211-1222[Abstract].
-
McKenzie JC,
Cowie RJ,
Inagami T
(1990)
ANP-like immunoreactivity in neuronal perikarya and processes associated with vessels of the pia and cerebral parenchyma in dog.
Neurosci Lett
117:253-258[Medline].
-
McKenzie JC,
Berman NEJ,
Thomas CR,
Young JK,
Compton LY,
Cothran LN,
Liu W-L,
Klein RM
(1994)
Atrial natriuretic peptide-like immunoreactive (ANP-LIR) neurons and astroglia of the human cerebral cortex.
Glia
12:228-243[Web of Science][Medline].
-
McKenzie JC,
Juan YW,
Thomas CR,
Berman NE,
Klein RM
(2001)
Atrial natriuretic peptide-like immunoreactivity in neurons and astrocytes of human cerebellum and inferior olivary complex.
J Histochem Cytochem
49:1453-1467[Abstract/Free Full Text].
-
Nogami M,
Shiga J,
Takatsu A,
Endo N,
Ishiyama I
(2001)
Immunohistochemistry of atrial natriuretic peptide in brain infarction.
Histochem J
33:87-90[Medline].
-
Parpura V,
Basarky TA,
Liu F,
Jeftinija K,
Jeftinija S,
Haydon PG
(1994)
Glutamate-mediated astrocyte-neuronal signalling.
Nature
369:744-747[Medline].
-
Parpura V,
Fang Y,
Basarsky T,
Jahn R,
Haydon PG
(1995)
Expression of synaptobrevin II, cellubrevin and syntaxin but not SNAP-25 in cultured astrocytes.
FEBS Lett
377:489-492[Web of Science][Medline].
-
Pasti L,
Zonta M,
Pozzan T,
Vicini S,
Carmignoto G
(2001)
Cytosolic calcium oscillations in astrocytes may regulate exocytotic release of glutamate.
J Neurosci
21:477-484[Abstract/Free Full Text].
-
Samson WK
(1987)
Atrial natriuretic factor and the central nervous system.
Endocrinol Metab Clin North Am
16:145-161[Web of Science][Medline].
-
Schwartz JP,
Wilson DJ
(1992)
Preparation and characterization of type 1 astrocytes cultured from adult rat cortex, cerebellum and striatum.
Glia
5:75-80[Web of Science][Medline].
-
Smith CB,
Betz WJ
(1996)
Simultaneous independent measurement of endocytosis and exocytosis.
Nature
380:531-534[Medline].
-
Sonnenberg H,
Veress AT
(1984)
Cellular mechanism of release of atrial natriuretic factor.
Biochem Biophys Res Commun
124:443-449[Web of Science][Medline].
-
Tanaka I, Inagami T (1986) Release of immunoactive atrial
natriuretic factor from rat hypothalamus in vitro 122:353-355.
Copyright © 2003 Society for Neuroscience 0270-6474/03/2351580-04$05.00/0
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J. Neurosci.,
September 28, 2005;
25(39):
8995 - 9004.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
T. Fellin and G. Carmignoto
Neurone-to-astrocyte signalling in the brain represents a distinct multifunctional unit
J. Physiol.,
August 15, 2004;
559(1):
3 - 15.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
V. Montana, Y. Ni, V. Sunjara, X. Hua, and V. Parpura
Vesicular Glutamate Transporter-Dependent Glutamate Release from Astrocytes
J. Neurosci.,
March 17, 2004;
24(11):
2633 - 2642.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
L. M. Garcia-Segura and M. M. McCarthy
Minireview: Role of Glia in Neuroendocrine Function
Endocrinology,
March 1, 2004;
145(3):
1082 - 1086.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
N. H. Barmack, T. R. Bilderback, H. Liu, Z. Qian, and V. Yakhnitsa
Activity-Dependent Expression of Acyl-Coenzyme A-Binding Protein in Retinal Muller Glial Cells Evoked by Optokinetic Stimulation
J. Neurosci.,
February 4, 2004;
24(5):
1023 - 1033.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
TOP
ABSTRACT
Introduction
