CL(-)CHANNELS ARE RANDOMLY ACTIVATED BY CONTINUOUS GABA SECRETION IN CULTURED EMBRYONIC RAT HIPPOCAMPAL-NEURONS

Throughout the adult vertebrate central nervous system (CNS) gamma-ami nobutyric acid (GABA) mediates transient Cl- conductances commonly ide ntified as fast, Cl--dependent inhibitory synaptic signals [Prog. Neur obiol., 36 (1991) 35 92]. In the rat hippocampus Cl--dependent excitat ory transients mediated by GABA emerge during the first postnatal week superimposed on a steady-state baseline that is also Cl-- and GABA-de pendent [Int. J.Dev. Neurosci., 8 (1990) 481-490]. Here we report that many embryonic rat hippocampal neurons cultured for hours to days exh ibit random fluctuations in Cl- channel activity that are mediated by continuous secretion of GABA in the absence of transients. Thus, GABA is broadcast tonically before it is released transiently.