Effect of vasopressin-like peptides on consumption of ethanol by the rat.

Rats were trained to accept ethanol in their drinking water, by successive small increments or decrements in alcohol concentration in response to the individual consumption of each rat. Those injected with desglycinamide9-lysine8-vasopressin (DGLVP), 1--4 microgram SC every second day, attained almost twice as high a final acceptance concentration (FAC) and mean daily ethanol intake (g/kg) as vehicle-treated controls. Hypophysectomized animals initially accepted the same alcohol concentrations as intact rats, but drank much larger volumes and correspondingly higher daily g/kg intakes. However, this was rapidly succeeded by rejection of all but very low concentrations, which was unaffected by DGLVP. During a subsequent free-choice period (water vs. ethanol at individual FACs), the groups maintained their relative positions with respect to ethanol intake. This was not altered by injection of vasopressin in the hypophysectomized rats, but was overcome by raising the alcohol concentration. The results suggest that vasopressin-like peptides facilitate acquisition of alcohol drinking behavior.