Effects of Administration of Adrenocorticotropin, Corticosteroids and Adrenal Inhibitor Metyrapone on Adrenocortical, Pineal and Gonadal Activity in Nocturnal bird, Athene brama and Diurnal bird, Perdicula asiatica

Abstract

Present study showed effects of adrenal gland modulation on adrenocortical, pineal and gonadal activity in two Indian tropical male and female birds belonging to nocturnal (Spotted owlet, Athene brama) and diurnal (Jungle bush quail, Perdicula asiatica) habitats. Administration of adrenocorticotropin (ACTH) to both sexes of nocturnal or diurnal bird during regressive or active and inactive phases of the reproductive cycle elevated adrenal and gonadal weights when compared to vehicle control groups. Pineal mass showed no change for the ACTH treatment in the regressive phase while it decreased significantly in the inactive phase. Administration of ACTH elevated the adrenocortical function during the inactive phase in both species, which becomes evident from the increase in adrenal lipids and plasma corticosterone level. Conversely, ACTH treatment during peak adrenal activity (regressive phase in owlet and active phase in quail) decreased the adrenal free cholesterol (FC) while increased adrenal phospholipids (PL) and esterified cholesterol (EC) levels in both species. However, plasma corticosterone levels after the ACTH treatment did not show any change. Administration of corticosterone and dexamethasone to both sexes of nocturnal birds during the regressive phase decreased the gonadal weights while the adrenal gland mass showed no change. Dexamethasone treatment alone reduced the pineal gland mass in females. In diurnal birds, corticosteroids produced no change in adrenal, gonadal and pineal gland weights. However, corticosteroids elevated PL and EC in both species while adrenal FC was unaltered in the nocturnal bird but decreased in the diurnal bird. Administration of adrenal gland inhibitor, metyrapone, to both sexes of the diurnal bird reduced adrenal and gonadal weights and adrenal lipids while it elevated the pineal gland mass. However, in nocturnal birds, the treatment altered only adrenocortical function. These results indicated that adrenal gland modulation possibly evoked a feedback response from the gland depending on the phase of reproductive (or adrenal) cycle and through this it altered pineal and gonadal activity differentially. Modulation of adrenal activity by ACTH produced a profound reduction in the pineal gland mass during the inactive phase of the reproductive cycle in both sexes of nocturnal and diurnal bird. Changes induced in the adrenocortical function also reflected to some extent on gonadal activity in both regressive/active and inactive phases of reproductive cycle in both species.