EPIDERMAL HYPERPLASIA IN INCUBATION PATCH OF CALIFORNIA QUAIL LOPHORTYX CALIFORNICUS IN RELATION TO PITUITARY PROLACTIN CONTENT

Prolactin causes hyperplasia of the incubation patch epidermis of the California quail (Lophortyx californicus) in vivo and in vitro. A comparison of the condition of this tissue with pituitary prolactin content revealed interesting relationships between synthesis and release of this hormone throughout the quail reproductive cycle. In females, prolactin content was low during egg laying and early incubation but high during brooding. Caged egg-laying females had eight times more prolactin than did wild egg-laying females. Comparison of these results with epidermal thickness indicated that the incubation of eggs stimulates release of prolactin from the pituitary. In males, prolactin content was low when the testes were inactive but was high in breeding males and males with regressing testes and an incubation patch. The condition of the epidermis in these birds suggested that circulating prolactin levels were high only in the last group, possibly in response to the presence of an abandoned nest. © 1969.