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Diazepam prevents changes in intracellular Cl − and Ca 2+ and restores neuronal activity after ischemia in vitro
Author(s) -
Galeffi F.,
Sah R.,
SchwartzBloom R. D.
Publication year - 2002
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.1471-4159.81.s1.42_12.x
Subject(s) - intracellular , hippocampal formation , muscimol , population spike , chemistry , population , biophysics , hippocampus , calcium in biology , endocrinology , medicine , ischemia , agonist , neuroscience , biology , biochemistry , receptor , environmental health , dentate gyrus
We have shown that diazepam (DZ) protects hippocampal neurons when administered early after transient cerebral ischemia. To examine mechanisms of DZ action, in the absence of systemic effects, we used an in vitro model of ischemia [oxygen‐glucose deprivation (OGD)] in the adult hippocampal slice. We are interested in determining if DZ can prevent upstream events such as loss of ionic homeostasis and its consequences on neuronal transmission. We measured the effect of OGD on changes in intracellular Cl − and Ca 2+ . Application of DZ after OGD prevented the increase in intracellular Cl − in area CA1 pyramidal neurons, measured by optical imaging with the Cl − sensitive fluorescent probe, MEQ. The increase in intracellular Cl − after OGD led to a reduction in GABA responses 2 h later, measured in the presence of the GABA agonist, muscimol. When DZ was added for 1 h after OGD, muscimol responses were restored completely. To measure changes in intracellular Ca 2+ after OGD, we bath‐loaded adult hippocampal slices with calcium green‐1 AM. OGD increased intracellular Ca 2+ in CA1 pyramidal neurons. The addition of DZ prior to OGD reduced the increase in intracellular Ca 2+ by approximately 50%. To determine the effect of DZ on neuronal transmission within the hippocampus, we measured field responses in area CA1 pyramidal neurons. Area CA1 population spikes were suppressed by OGD and they did not recover 1 h later. When DZ was included in the reoxygenation buffer for only 30 min, it restored the population spike amplitude to within 85% of that in normal slices. Thus, after OGD, DZ restores ionic homeostasis, preserves GABA responses and restores neuronal activity within the hippocampus. Acknowledgements: Supported by NIH grant #NS28791.