Endocrine profile during acquisition of free-choice alcohol drinking in rhesus monkeys; treatment with desglycinamide-(Arg8)-vasopressin.

This study concerns the effect of spontaneous acquisition of alcohol drinking in rhesus monkeys on plasma levels of beta-endorphin, ACTH, prolactin, cortisol and testosterone. Twelve monkeys had free-choice access to water and two ethanol/water solutions (1%, 2%, v/v) for 4 weeks. During the first 2 weeks, six monkeys were injected (i.m.) twice daily with 0.50 microgram/kg desglycinamide-(Arg8)-vasopressin (DGAVP), a neuropeptide, that has been postulated to interfere with central positive reinforcement processes. The other six were treated with a placebo. Hormonal plasma levels after the first 2 weeks and after another 2 weeks of alcohol drinking were compared to pre-alcohol hormonal levels (baseline). The placebo-treated subjects significantly increased, but the DGAVP-treated subjects significantly decreased ethanol intake over time. After 2 weeks of alcohol, significant increases were found in beta-endorphin and ACTH levels. After 4 weeks, prolactin was increased, cortisol decreased and particularly beta-endorphin remained significantly increased. No relationship was found between baseline hormonal levels and subsequent ethanol intake. No significant differences in plasma hormonal changes were observed between DGAVP- and placebo-treated subjects. Two placebo-treated subjects that showed the highest increase in ethanol intake over time, reacted differently, by reducing beta-endorphin and ACTH levels over time, showing the largest decreases in cortisol and hardly any prolactin reaction. It is concluded that spontaneous alcohol drinking by naïve subjects disturbs hormonal processes and that two animals deviated with respect to the acquisition in alcohol drinking and endocrine functioning.