The action of picrotoxin on the interspike interval in rat supraoptic neurones

Effects of gamma-aminobutyric acid (GABA) antagonists on cells of the supraoptic nucleus have been investigated in isolated slices of rat hypothalamus. Bicuculline had no effect on firing patterns or the minimum interspike interval. Picrotoxin reduced the minimum interspike interval and caused long-lasting bursts of high-frequency spikes, an effect that persisted even when synaptic transmission was blocked. We suggest, that in this case, picrotoxin is not acting primarily as a GABA antagonist but as a blocker of chloride channels, thereby altering the cell properties that regulate the minimum interval.