SEX DIFFERENCE IN DAILY WATER-CONSUMPTION OF RATS - EFFECT OF HOUSINGAND HORMONES

Females rats consume more water than males per day when consumption is indexed to body weight. We examined the developmental expression of t his sex difference as well as the organizational and activational infl uences of testosterone (T). The amount of water consumed from weaning to adulthood exhibited a linear decrease with age in both sexes. The d evelopment of a sex difference in water consumption was evident immedi ately after weaning in singly housed animals, but did not emerge until about Day 42-45 in group-housed animals, when females began to consum e greater amounts of water than males. Castration at weaning had minim al effects on the sex difference. Treating dams with testosterone prop ionate (TP; 0.3 mg/kg; E15-E20) resulted in a significant increase in adult water consumption in offspring of both sexes, but the sex differ ence remained. Overall, these data indicate that gonadal steroids are not the primary organizational influence on this sex difference. The g reater water consumption in females is consistent with other studies d emonstrating sex differences in plasma vasopressin levels, as well as differences in vasopressin sensitivity.