Pituitary-adrenal and dopaminergic modulation of schedule-induced polydipsia: behavioral and neurochemical evidence.

Five experiments investigated in rats the effects of increasing or decreasing plasma corticosterone levels on schedule-induced polydipsia and dopamine efflux in the nucleus accumbens. The results indicate that the acquisition of schedule-induced polydipsia could be decreased by adrenalectomy, blockade of corticosterone synthesis, or administration of corticosterone. Performance of established schedule-induced polydipsia was also decreased by adrenalectomy. The effects of corticosterone administration on established schedule-induced polydipsia depended on the level of performance. High levels of drinking were enhanced by a high dose of corticosterone, whereas low rates of drinking were increased by a low dose. Similar injections of corticosterone also significantly increased dopamine efflux. The relative involvement of pituitary-adrenal activity and dopamine neurotransmission in the nucleus accumbens in the acquisition and performance of SIP is discussed and related to contemporary hypotheses of schedule-induced behavior.