argipressin--des-glynh2(9)- and 3-hydroxybenzylhydrazine

Central tolerance to the effects of ethanol in rats can be prolonged beyond its normal time of disappearance by administration of vasopressin (AVP) or desglycinamide-arginine-vasopressin (DGAVP) after ethanol withdrawal. While the mechanism underlying this effect is unknown, we have reported that specific depletion of hippocampal serotonin (5-HT) prevents the prolongation of tolerance by DGAVP. The present study explored possible presynaptic interactions between DGAVP and 5-HT terminals in the hippocampus, in relation to tolerance retention. When administered acutely, DGAVP had no effect on the rates of hippocampal or septal 5-HT synthesis in naive rats, as assessed by the NSD 1015 method. Moreover, chronic DGAVP treatment that maintained tolerance did not change the in vivo rate of 5-HT synthesis in the hippocampus or septum. Similarly, no significant differences were found in the levels of hippocampal 5-HT or 5-HIAA. Septal 5-HIAA levels were slightly but significantly lower in ethanol-DGAVP than in ethanol-saline rats. In vitro studies revealed, on the other hand, that addition of AVP to the incubation medium failed to affect the spontaneous and stimulated release of endogenous 5-HT from hippocampal slices. While the lack of changes in hippocampal 5-HT synthesis argues against a presynaptic DGAVP-5-HT interaction, the possibility remains of a peptide modulation of 5-HT postsynaptic actions.

Topics: 5-Hydroxytryptophan; Animals; Arginine Vasopressin; Drug Tolerance; Ethanol; Hippocampus; Hydrazines; Hydroxyindoleacetic Acid; In Vitro Techniques; Male; Motor Activity; Rats; Rats, Inbred Strains; Septum Pellucidum; Serotonin