Tetanus-induced asynchronous GABA release in cultured hippocampal neurons

Asynchronous GABA release was studied in cultured hippocampal neurons using paired whole-cell recordings. Tetanization of the presynaptic GABAergic ne uron was accompanied by a train of IPSCs which showed tetanic depression. A synchronous IPSCs (asIPSCs) also developed during the train and continued f or 1.85+/-0.3 s after the stimulation. The threshold frequency for evoking asIPSCs was 10 Hr,. while maximal asynchronous activity was achieved at 40 Hz. Perfusion with EGTA-AM blocked asIPSCs. The elevation of [Ca2+](i) that accompanies presynaptic action potential firing triggers asynchronous rele ase of GABA vesicles, thereby counteracting tetanic depression of synchrono us IPSCs. (C) 2000 Elsevier Science B.V. All rights reserved.