No evidence for diurnal variation in the responsiveness of the pituitary-adrenocortical axis of the pigeon (Columba livia domestica) to stimulation with adrenocorticotrophin and vasopressin.

The responsiveness of the pituitary-adrenocortical axis of the pigeon (Columba livia domestica) to intravenous administration of high and low doses of adrenocorticotrophic hormone (ACTH) and following arginine vasopressin (AVP) was investigated at two different moments of the diurnal rhythm. Administrations of ACTH and AVP were performed at the moment of low plasma corticosterone concentration and during high plasma corticosterone concentration. Plasma corticosterone concentrations following administration of AVP and ACTH did not change with the time of the day. It is concluded that for the assessment of pituitary adrenocortical function in pigeons the pituitary adrenocortical stimulation tests with AVP and ACTH can be used at any time of day.