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Decreased Hippocampal Expression, but Not Functionality, of GABA B Receptors After Transient Cerebral Ischemia in Rats
Author(s) -
Francis Joseph,
Zhang Yu,
Ho Warren,
Wallace M. Christopher,
Zhang Liang,
Eubanks James H.
Publication year - 1999
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1046/j.1471-4159.1999.0720087.x
Subject(s) - hippocampal formation , excitatory postsynaptic potential , gabab receptor , receptor , medicine , endocrinology , baclofen , gabaa receptor , electrophysiology , neuroscience , biology , in situ hybridization , granule cell , receptor expression , gene expression , chemistry , pharmacology , dentate gyrus , agonist , biochemistry , gene
: We have examined the effects of transient global ischemiaon both the gene expression levels and the functionality of GABA B receptors in rat brain, using antisense in situ hybridization andelectrophysiological evaluations. At the level of gene expression, nosignificant change in GABA B receptor expression was observed in anyhippocampal subfield at either 6 or 12 h after challenge. At 24 hpostchallenge, however, a significant decrease in GABA B receptorexpression was observed in both the CA1 and CA3 subfields, whereas no changewas observed in the dentate granule cell layer. Although expression in boththe vulnerable CA1 and less vulnerable CA3 subfields was diminished at thistime postchallenge, there was no significant difference in the degree of thediminished expression between these subfields. At the functional level, thedose‐dependent ability of baclofen (1‐100 μ M ) to inhibit an evokedexcitatory postsynaptic potential (f‐EPSP) in the CA1 subfield was evaluatedat 24 h postischemia, in comparison with the dose‐response observed insham‐operated subjects. No significant differences were observed in theefficacy of GABA B receptor‐mediated inhibition of the elicitedf‐EPSP at any of the baclofen concentrations examined. These data demonstratethat although the mRNA expression levels for the GABA B receptor arediminished in both vulnerable and less vulnerable neurons of Ammon's horn at24 h following transient global ischemia, the functionality of theGABA B receptor system is maintained at this time postchallenge.