A BENZODIAZEPINE, CHLORDIAZEPOXIDE, BLOCKS VASOPRESSIN AND OXYTOCIN RELEASE AFTER FOOTSHOCKS BUT NOT OSMOTIC STIMULUS IN THE RAT

Noxious as well as hypertonic stimuli potentiate vasopressin and oxyto cin secretion in rats. Neurohypophysial vasopressin- and oxytocin-secr eting neurons receive inhibitory synaptic inputs mediated by gamma-ami nobutyric acid (GABA). Benzodiazepines modulate GABA-A receptor activi ty in a facilitatory fashion. it is thus possible that benzodiazepines suppress vasopressin and oxytocin release after noxious stimuli. To t est this hypothesis, we investigated whether chlordiazepoxide impairs the enhanced release of vasopressin and oxytocin after noxious or hype rtonic stimuli in male rats. Chlordiazepoxide (5-20 mg/kg, i.p.) block ed dose-dependently the vasopressin and oxytocin responses to footshoc ks. Chlordiazepoxide, however, did not impair the hormonal responses t o hypertonic stimulus. The results demonstrate that chlordiazepoxide s electively prevents vasopressin and oxytocin release after noxious sti muli and therefore suggest that the sites of chlordiazepoxide actions are not on the vasopressin or oxytocin neurons in rats.