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Adrenal cortical and medullary responses to acetylcholine and vasoactive intestinal peptide in conscious calves.
Author(s) -
Edwards A V,
Jones C T
Publication year - 1993
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.1993.sp019785
Subject(s) - vasoactive intestinal peptide , acetylcholine , endocrinology , medullary cavity , medicine , vasoactive , neuroscience , biology , neuropeptide , receptor
1. Adrenal responses to intra‐aortic infusions of acetylcholine and vasoactive intestinal peptide (VIP) have been investigated in functionally hypophysectomized calves given exogenous adrenocorticotrophic hormone (ACTH, 2 ng min‐1 kg‐1 I.V.). 2. Infusions of VIP at a dose of 0.13 micrograms min‐1 kg‐1 caused a small, but significant increase in adrenaline and noradrenaline output which was, however, far below the level recorded previously in response to acetylcholine (0.7 micrograms min‐1 kg‐1). In contrast, these doses of the two agonists produced closely similar rises in adrenal cortisol output. 3. The steroidogenic effects of acetylcholine and VIP were found to be strictly additive and no evidence of potentiation was obtained in relation to either cortical or medullary responses or in the case of any of the cardiovascular responses which were monitored. 4. Intra‐aortic infusions of VIP, at a dose which produced a substantial increase in adrenal steroidogenesis (0.065 micrograms min‐1 kg‐1), had no effect on the output of catecholamines, enkephalin‐like immunoreactivity or corticotrophin‐releasing factor, either in the presence or absence of acetylcholine. 5. It is concluded that VIP is unlikely to modulate adrenal medullary responses to muscarinic stimulation in this species as it has been claimed to do in the rat and does not potentiate adrenal steroidogenesis in response to acetylcholine as it does to ACTH.