Localization of progesterone receptor in brain and pituitary of the ring dove: influence of breeding cycle and estrogen.

An immunocytochemical method was used in male and female ring doves (Streptopelia risoria) to localize progesterone receptor immunoreactivity (PR-ir) in the brain and anterior pituitary gland in nonbreeding, incubating, brooding, and estrogen (E2)-treated nonbreeding birds. Progesterone receptor was found in four regions of the brain in males and females: the preoptic area (POA), nucleus preopticus paraventricularis magnocellularis (PPM), nucleus hypothalami lateralis (PLH), and the tuberal region (TR). Quantitative analysis demonstrated that the density of cell nuclei containing PR-ir in the POA, PPM, and PLH in brooding birds was significantly higher than in E2-treated doves or in birds at other stages of the reproductive cycle. The density of PR-containing cell nuclei in the TR of male ring doves was significantly higher on day 1 of incubation than in nonincubating males. In brooding birds, there was a significant decrease in PR-ir in the TR, particularly in the ventral region where nuclei containing PR-ir disappeared. In the anterior pituitary gland the density of cell nuclei containing PR-ir was higher in females than in males at the onset of incubation. E2 treatment resulted in an increase in the density of PR-containing cell nuclei in both males and females. Brooding females had a lower concentration of PR-containing cell nuclei than did females at other stages of the breeding cycle. It is suggested that progesterone receptor in the POA mediates the expression of incubation behavior while progesterone receptor in the TR is involved in the control of neuroendocrine function. The source of estrogen which increases PR appears to be of central nervous origin in the male and may be predominantly peripheral in the female.