AJP - Endocrinology and Metabolism, Vol 242, Issue 4 215-E219, Copyright © 1982 by American Physiological Society
Developmental aspects of pituitary and adrenal responses to arterial hypotension in neonatal, weanling, and adult sheep
J. C. Rose, M. Morris and P. J. Meis
We have studied neuroendocrine and heart rate responses to arterial
hypotension in unanesthetized, chronically cannulated neonatal (less than
10 days old), weanling (3- to 4-wk-old), and adult sheep.
Nitroprusside-induced arterial hypotension in the absence of hypovolemia
promptly increased plasma ACTH, vasopressin (AVP), and cortisol levels in
all three groups. The integrated adenohypophyseal and neurohypophyseal
responses to a standard hypotensive stimulus were similar at the three
ages, suggesting that the functional development of the systems subserving
these responses is complete by the immediate postnatal period. The
integrated cortisol/ACTH ratio was greatest in the youngest animals,
suggesting that enhanced adrenal responsiveness to ACTH exists in neonatal
as well as in late-gestation fetal lambs. The reflex tachycardia
accompanying the arterial hypotension in the weanling and adult sheep was
absent in the neonates.
