Adrenal responses to the peptide PACAP in conscious functionally hypophysectomized calves.
Intra-aortic infusions of pituitary adenylate cyclase-activating peptide-(1-38) (PACAP) produced a dose-related fall in aortic blood pressure over the range of 4-40 pmol.min-1.kg-1 in the presence of exogenous adrenocorticotropic hormone-(1-24) (ACTH, 2 ng.min-1.kg-1 i.v.; P < 0.01). At the higher dose there was a significant fall in adrenal vascular resistance in the absence, but not in the presence, of ACTH. PACAP also produced a dose-related increase in right adrenal cortisol output over the same range, which was significantly greater in the absence of exogenous ACTH (P < 0.01). At the higher dose, PACAP produced small but significant increases in adrenal epinephrine and norepinephrine output (P < 0.01) both in the presence and the absence of ACTH. There was also a small rise in Met5-enkephalin output, and corticotrophin-releasing factor (CRF) was released in the presence, but not in the absence, of ACTH. It is concluded that PACAP is capable of exerting potent steroidogenic and vasodilator effects in the adrenal gland in the normal conscious calf and of releasing significant amounts of catecholamines, enkephalins, and CRF from the adrenal medulla. These findings identify PACAP as a candidate neuromodulator in the adrenal gland in this species.
Physiological Laboratory, University of Cambridge, United Kingdom.
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Edwards
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Jones
D000302:Adrenal Cortex / Q000187:drug effects; D000311:Adrenal Glands / Q000187:drug effects* / Q000378:metabolism; D000313:Adrenal Medulla / Q000187:drug effects; D000324:Adrenocorticotropic Hormone / Q000494:pharmacology; D000818:Animals; D002319:Cardiovascular System / Q000187:drug effects; D002417:Cattle; D003346:Corticotropin-Releasing Hormone / Q000378:metabolism; D004744:Enkephalin, Methionine / Q000378:metabolism; D004837:Epinephrine / Q000378:metabolism; D007016:Hypophysectomy; D009479:Neuropeptides / Q000494:pharmacology*; D009638:Norepinephrine / Q000378:metabolism; D051219:Pituitary Adenylate Cyclase-Activating Polypeptide
D009479:Neuropeptides; D051219:Pituitary Adenylate Cyclase-Activating Polypeptide; D004744:Enkephalin, Methionine; D000324:Adrenocorticotropic Hormone; D003346:Corticotropin-Releasing Hormone; D009638:Norepinephrine; D004837:Epinephrine