The relationship between schedule-induced polydipsia and pituitary-adrenal activity: pharmacological and behavioral...

The relationship between schedule-induced polydipsia (SIP) and pituitary-adrenal activity in rats was investigated using two different approaches that involved either capitalizing on pre-existing individual differences in the propensity to show SIP, or by inducing differences in plasma corticosterone by behavioral or pharmacological means. Thus, in Expt. 1, SIP was monitored after corticosterone levels were pharmacologically altered with drugs that act at the benzodiazepine receptor. In Expt. 2, the relationship between individual differences in water consumption during SIP and plasma corticosterone levels was determined. In addition, corticosterone levels were determined after the prevention of drinking during SIP. Results indicated an inverse relationship between plasma corticosterone levels and SIP. It was also found that corticosterone levels were significantly higher following SIP with water available than after SIP without water. The implications of these results for previous hypotheses of SIP are discussed.