NO EVIDENCE FOR DIURNAL-VARIATION IN THE RESPONSIVENESS OF THE PITUITARY-ADRENOCORTICAL AXIS OF THE PIGEON (COLUMBA-LIVIA DOMESTICA) TO STIMULATION WITH ADRENOCORTICOTROPIN AND VASOPRESSIN

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