J. Vautrin et al., TONIC GABA SECRETION OF CULTURED RAT HIPPOCAMPAL-NEURONS RAPIDLY TRANSFORMED BY ZN-2+ INTO QUANTAL RELEASE, Neuroscience letters, 158(2), 1993, pp. 125-129
Different mechanisms of neurotransmitter secretion at synapses have be
en ascribed to quantal, transient signals [4-9] and to continuous, ton
ic activity [11, 21, 25]. Quantal transmission is imputed to be the re
lease of transmitter packets, or quanta [6], assembled and stored in v
esicles present in presynaptic terminals [2, 8]. We report that 300 mu
M Zn2+ rapidly transformed tonic Cl- conductance mediated by the trans
mitter gamma-aminobutyric acid (GABA) into transient synaptic-like sig
nals. After addition of Zn2+, the size of the elementary fluctuations
in the Cl- current progressively increased while randomly activated Cl
- channel kinetics remained unchanged and accounted for the bi-exponen
tial time course of average transient decay. The results suggest that
Zn2+ rapidly transforms tonic GABA secretion into quantal-like transie
nt release.