THAPSIGARGIN INHIBITS BICUCULLINE-INDUCED EPILEPTIFORM EXCITABILITY IN RAT HIPPOCAMPAL SLICES

Evoked field potentials were recorded in the CA3 region of rat hippoca mpal slices to detect whether intracellular Ca2+ stores are involved i n the epileptiform effects of the two prototypic GABA(A) antagonists, bicuculline methiodide (BMI) and gabazine (SR-95531; GBZ). Field popul ation spikes gradually increased and became repetitive (epileptiform b ursting) in the presence of either BMI (5 mu M), or GBZ (5 mu M). Thap sigargin (2 mu M), a depletor of intracellular Ca2+ stores, reduced th e epileptiform effect of BMI, but had no significant effect on the GBZ -induced hyperexcitability. These data suggest that Ca2+ release from intracellular stores participates in the epileptiform response of hipp ocampal CA3 neurons to BMI, but not in the response to GBZ. (C) 1998 E lsevier Science Ireland Ltd.