Stimulus-evoked efflux of GABA from preloaded slices of the rabbit oviduct

The effect of electrical and chemical stimulation on the efflux of [3H]gamma-aminobutyric acid (GABA) from preloaded slices of the rabbit oviduct was examined. Electrical field stimulation significantly increased the outflow of [3H]GABA. This effect could not be prevented by tetrodotoxin or by the removal of Ca2+ from the medium. High K+ concentrations, veratrine and ethylenediamine also evoked a remarkable elevation in the efflux. The release induced by veratrine was completely abolished in a Ca2+-free medium or in the presence of tetrodotoxin, while the release evoked by high K+ or ethylenediamine was resistant to both conditions. These findings indicate that GABA can be released from the oviduct under the effect of depolarizing stimuli, raising the possibility of a physiological interaction between oviductual GABA and its receptors. The characteristics of oviductal GABA efflux differ from those of neuronal and glial GABA release.