Seasonal changes in adrenal and gonadal activity in the quail, Perdicula asiatica: involvement of the pineal gland

The present study assessed annual adrenal gland activity in the Indian trop ical Jungle bush quail, Perdicula asiatica. We also elucidated the role of the annual variations in gonadal steroids and melatonin in the regulation o f its activity. Increasing day length (photoperiod), ambient temperature an d rainfall are positively correlated with adrenal and gonadal functions, an d inversely related to pineal gland activity. Pineal, adrenal and gonadal w eights showed cyclical patterns relative to environmental factors, which we re also correlated with plasma melatonin, corticosterone and gonadal steroi ds, respectively. In both sexes of P. asiatica, pineal gland weight and/or plasma melatonin levels were inversely related to adrenal lipids, (e.g. pho spholipids, free and esterified cholesterol) and plasma corticosterone leve ls. Melatonin levels also showed an inverse relationship with plasma testos terone and estradiol levels. These studies indicate that changes in environ mental factors promote annual variations in adrenal and gonadal activity pr obably by modulating the pineal gland. Melatonin receptors have been locali zed in the pars tuberalis, adrenal gland and gonads of birds, the pineal gl and may, therefore, mediate environmental stimuli indirectly and directly t o down regulate adrenal and gonadal. activity, which run in parallel in thi s species. (C) 2001 Elsevier Science Inc. All rights reserved.