Functional development of the hypothalamo‐hypophyseal‐adrenal cortex axis in the chick embryo, Gallus domesticus

Abstract

Basal plasma levels of corticosterone increased gradually during the second half of incubation, reaching a peak around the time of hatching. Stress resulted in a very significant elevation of corticosterone above the basal level in embryos 16 days or older, but not in younger embryos. Newly hatched chicks did not respond to stress, but a typical stress response was evident one week after hatching. Adrenocorticotropin (100 mu) elicited a significant rise in plasma corticosterone in 14-day embryos and in newly hatched chicks, demonstrating that the adrenal is capable of responding to pituitary stimulation at these times when a stress response does not occur.Decapitated 16-day embryos had significantly lower basal levels of corticosterone than normal, and showed no rise in corticosterone in response to stress. Basal levels of corticosterone were unaffected by decapitation of 14-day embryos. Grafting ten-day embryonic pituitaries to the chorioallantoic membrane on day 9 of incubation restored normal basal hormone levels on day 16 in decapitated embryos, but did not restore the ability to respond to stress.This study demonstrates that the hypothalamo-hypophyseal-adrenal axis is functional before hatching in chicks. The adrenal exhibits significant autonomous functional capability prior to day 14, and the pituitary becomes important in maintaining both the resting level of hormone and the stress response between days 14 and 16 of incubation. The hypothalamus does not appear to control normal resting levels of corticosterone, but is essential for the stress response. It was partially supported by a Rackham Graduate Student Dissertation grant h o m the University of Michigan.

Dry season juvenile growth and physiological parameters in exotic and Nigerian indigenous chicken

“…The similarity in the levels of plasma corticosterone observed at day old in all the strains of the birds used in this study indicates that they were not yet stressed and the environmental influence had not been imposed on them. An increase in plasma corticosterone levels with increasing age of chicks up to 7-daypost-hatch has been reported (Tona et al, 2003;Wise and Fry, 1973;Tona et al, 2005). In agreement with these previous studies, our results show increasing concentrations of corticosterone up to 7-day-post-hatch in the NIC.…”

Lung Development in the Chick Embryo II. Choline and Ethanolamine Kinase Activity in the Developing Lungs of Normal and Hypophysectomized Chick Embryos

“…Differences in activities of both enzymes were detected between the lungs of normal and hypophysectomized chick embryos on day 16. At this time, a significant decrease in circulating levels of corticosterone is seen in the hypophysectornized embryo (36). CK and EK activites remain elevated for most of the remainder of the incubation period in the lungs of hypophysectornized chick embryos.…”

“…Although pituitary control of endocrine glands does not occur in the rat fetus until 17 days of gestation (23), some glands may be capable of earlier hormonal secretion. For example, in the chick embryo, the adrenal cortex can secrete autonomously as early as 5 days before pituitary regulation occurs (36). If the same is true in the developing mammalian adrenal cortex, then some circulating glucocorticoids may already be present at the time of hypophysectomy.…”

“…This response is dependent upon an intact hypothalamic-hypophyseal-adrenal axis, which is only present in the chick after 14 days of incubation (36). Removal of the chick pituitary primordium at 36 h of incubation eliminates the possibility of any hormonally mediated stress response of the embryo to the surgical procedure; thus, the developing chick lung is a good model system for examining endocrine effects without the confounding interactions of maternal and/or stress responses.…”

Physiological and Behavioral Responses of Young Chicks to High Ambient Temperature

“…A temporary loss in the ability to respond to stressors has been demonstrated in both neonatal mammals (Levine, 1970;Hiroshige and Sato, 1971;Guillet and Michaelson, 1978) and birds (Wise and Frye, 1973;Freeman and Manning, 1977;Freeman and Flack, 1980;Ramade and Baylé, 1980;Freeman, 1982). The cause of this unresponsiveness is uncertain but it has been suggested that it may be due to failure were determined by Dry-chem 7000 system (Fuji Medical System Co. Ltd., Japan; Catalog number: Fujifilm DRI-CHEM 7000).…”