Vasopressin and ethanol preference. I. Effects of vasopressin and the fragment DGAVP on altered ethanol preference in Brattleboro diabetes insipidus rats

Preference for concentrations of ethanol between 2.2 and 10 percent versus tap water was studied in Brattleboro rats homozygous for diabetes insipidus (di/di), heterozygous (di/+) or normal (+/+). The di/di rats, totally lacking in vasopressin, had greatly reduced preference scores for all concentrations of ethanol. Their intake of ethanol (g/day) was higher than heterozygotes or normals, but only when 2.2 percent ethanol was offered as a choice. Administration of lysine vasopressin or the vasopressin fragment des-9-Glycinamide-[Arginine⁸] vasopressin (DGAVP) using osmotic minipumps enhanced ethanol preference scores, reduced ethanol (g/day) intake, and restored total daily fluid intake in di/di rats. When di/di and di/+ rats were first allowed to develop stable ethanol preference before treatment with DGAVP, the peptide had no effect on preference scores. Thus, no treatment was effective in dissociating polydipsia from reduced ethanol preference and increased ethanol intake. While these results cannot exclude a possible regulatory role for endogenous vasopressin in ethanol preference drinking, they more strongly suggest that reduced preference for ethanol and increased ethanol intake are epiphenomena secondary to a polydipsic state.