Prolactin concentrations in the pituitary gland and plasma of Japanese quail in relation to photoperiodically induced sexual maturation and egg laying

A heterologous radioimmunoassay was used to measure pituitary and plasma concentrations of prolactin in Japanese quail (Coturnix coturnix japonica). The pituitary content increased significantly during photoperiodically induced sexual maturation and declined during gonadal regression on short days. Higher pituitary prolactin levels were attained in females than in males, and laying females had higher concentrations than nonlaying females. Plasma concentrations were similar in all groups. It is suggested that the high pituitary levels and the consistent plasma concentrations in laying females are related to the suppression of incubation behaviour in caged birds.