Inhibition of adrenocorticotrophin secretion during deprivation-induced eating and drinking in rats.

Rats that were maintained on a 23-h food and water deprivation schedule (food and water available between 09:00 and 10:00 h) for 21 days, and whose blood was sampled at various times following initiation of ingestion showed a decrease in plasma adrenocorticotrophin (ACTH) concurrent with dropping plasma levels of corticosterone (COR). This drop occurred from elevated levels of these hormones, most likely due to altered circadian patterns of pituitary-adrenal activity as a result of the rhythm-entraining properties of the feeding schedule. This inhibition of secretion of ACTH is interpreted as reflecting the inhibitory effect of a central nervous system mechanism that can affect ACTH secretion independently of corticosteroid negative feedback.