The effect of corticosterone on the photoperiodic response of immature hens

Abstract

White Leghorn pullets, 18 weeks of age, were infused with 30 μg/hr of corticosterone for 14 days. After 7 days of continuous infusion, the pullets were photostimulated by transfer from 8L:16D to 16L:8D. Noninfused controls were either photostimulated on Day 7 or remained on an 8L:16D photoschedule. Blood samples were obtained on 3, 6, 8, 10, and 12 days of infusion and were assayed for plasma concentrations of LH, estradiol, and corticosterone by radioimmunoassay. On Day 14 all birds were weighed and sacrificed, and the ovarian and oviducal weights were recorded. Photostimulation had no effect on plasma concentrations of corticosterone. The infusion of corticosterone significantly raised the plasma concentration to 5.2 ng/ml, suppressed the photo-induced rise in plasma concentrations of LH, and resulted in significantly lower plasma concentrations of estradiol. After 7 days of photostimulation either with or without corticosterone infusion, there were no significant differences in mean ovarian weight. The oviducal weight of hens infused with corticosterone was, however, significantly lowered. It is suggested that one of the mechanisms associated with the antigonadal effect of corticosterone involves an inhibition of Gn-RH release by the hypothalamus.