Tonic GABA secretion of cultured rat hippocampal neurons rapidly transformed by Zn2+ into quantal release.
Different mechanisms of neurotransmitter secretion at synapses have been ascribed to quantal, transient signals [4-9] and to continuous, tonic activity [11, 21, 25]. Quantal transmission is imputed to be the release of transmitter packets, or quanta [6], assembled and stored in vesicles present in presynaptic terminals [2,8]. We report that 300 microM Zn2+ rapidly transformed tonic Cl- conductance mediated by the transmitter gamma-aminobutyric acid (GABA) into transient synaptic-like signals. 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-exponential time course of average transient decay. The results suggest that Zn2+ rapidly transforms tonic GABA secretion into quantal-like transient release.
Vautrin
J
J
Laboratory of Neurophysiology, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892.
Schaffner
A E
AE
Barker
J L
JL
D000818:Animals; D002478:Cells, Cultured; D018118:Chloride Channels / Q000187:drug effects / Q000378:metabolism; D006624:Hippocampus / Q000187:drug effects / Q000378:metabolism*; D007700:Kinetics; D009474:Neurons / Q000187:drug effects / Q000378:metabolism*; D017729:Presynaptic Terminals / Q000187:drug effects; D051381:Rats; D013569:Synapses / Q000187:drug effects / Q000378:metabolism; D015032:Zinc / Q000494:pharmacology*; D005680:gamma-Aminobutyric Acid / Q000378:metabolism*
D018118:Chloride Channels; D005680:gamma-Aminobutyric Acid; D015032:Zinc