Astrocytes in adult rat brain express type 2 inositol 1,4,5-trisphosphate receptors

Astrocytes respond to neuronal activity by propagating Ca2+ waves elicited through the inositol 1,4,5‐trisphosphate pathway. We have previously shown that wave propagation is supported by specialized Ca2+ release sites, where a number of proteins, including inositol 1,4,5‐trisphosphate receptors (IP...

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Bibliographic Details
Published in:Glia 2002-07, Vol.39 (1), p.69-84
Main Authors: Holtzclaw, Lynne A., Pandhit, Siddhesh, Bare, Dan J., Mignery, Gregory A., Russell, James T.
Format: Article
Language:English
Subjects:
Amino Acid Sequence
Animals
Antibodies - chemistry
Antibodies - metabolism
astrocytes
Astrocytes - chemistry
Astrocytes - metabolism
Binding Sites, Antibody
Biological and medical sciences
Brain - metabolism
Calcium Channels - analysis
Calcium Channels - biosynthesis
Calcium Channels - immunology
Cerebellum - cytology
Cerebellum - metabolism
Fundamental and applied biological sciences. Psychology
Hippocampus - cytology
Hippocampus - metabolism
Immunohistochemistry
Inositol 1,4,5-Trisphosphate - metabolism
Inositol 1,4,5-Trisphosphate Receptors
IP3R2
Isolated neuron and nerve. Neuroglia
Male
Molecular Sequence Data
Rats
Rats, Sprague-Dawley
Receptors, Cytoplasmic and Nuclear - analysis
Receptors, Cytoplasmic and Nuclear - biosynthesis
Receptors, Cytoplasmic and Nuclear - immunology
Synapses - metabolism
Vertebrates: nervous system and sense organs
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Summary:Astrocytes respond to neuronal activity by propagating Ca2+ waves elicited through the inositol 1,4,5‐trisphosphate pathway. We have previously shown that wave propagation is supported by specialized Ca2+ release sites, where a number of proteins, including inositol 1,4,5‐trisphosphate receptors (IP3R), occur together in patches. The specific IP3R isoform expressed by astrocytes in situ in rat brain is unknown. In the present report, we use isoform‐specific antibodies to localize immunohistochemically the IP3R subtype expressed in astrocytes in rat brain sections. Astrocytes were identified using antibodies against the astrocyte‐specific markers, S‐100β, or GFAP. Dual indirect immunohistochemistry showed that astrocytes in all regions of adult rat brain express only IP3R2. High‐resolution analysis showed that hippocampal astrocytes are endowed with a highly branched network of processes that bear fine hair‐like extensions containing punctate patches of IP3R2 staining in intimate contact with synapses. Such an organization is reminiscent of signaling microdomains found in cultured glial cells. Similarly, Bergmann glial cell processes in the cerebellum also contained fine hair‐like processes containing IP3R2 staining. The IP3R2‐containing fine terminal branches of astrocyte processes in both brain regions were found juxtaposed to presynaptic terminals containing synaptophysin as well as PSD 95‐containing postsynaptic densities. Corpus callosum astrocytes had an elongated morphology with IP3R2 studded processes extending along fiber tracts. Our data suggest that PLC‐mediated Ca2+ signaling in astrocytes in rat brain occurs predominantly through IP3R2 ion channels. Furthermore, the anatomical arrangement of the terminal astrocytic branches containing IP3R2 ensheathing synapses is ideal for supporting glial monitoring of neuronal activity. GLIA 39:69–84, 2002. Published 2002 Wiley‐Liss, Inc.
ISSN:0894-1491
1098-1136
DOI:10.1002/glia.10085