Adrenal responses to the peptide PACAP in conscious functionally hypophysectomized calves

Area of Science:

• Endocrinology
• Neuroscience
• Physiology

Background:

• Pituitary adenylate cyclase-activating peptide (PACAP) is a neuropeptide with diverse physiological roles.
• The specific functions of PACAP within the adrenal gland require further elucidation.

Purpose of the Study:

• To investigate the effects of intra-aortic PACAP infusions on hemodynamic and adrenal parameters in conscious calves.
• To determine the influence of exogenous adrenocorticotropic hormone (ACTH) on PACAP's actions in the adrenal gland.

Main Methods:

• Intra-aortic infusions of PACAP-(1-38) were administered to conscious calves at varying doses.
• Hemodynamic parameters (aortic blood pressure, adrenal vascular resistance) and adrenal hormone outputs (cortisol, epinephrine, norepinephrine, Met5-enkephalin, CRF) were measured.
• Experiments were conducted both in the presence and absence of exogenous ACTH-(1-24).

Main Results:

• PACAP induced a dose-related decrease in aortic blood pressure and adrenal vascular resistance.
• PACAP stimulated cortisol output, with a greater effect in the absence of ACTH.
• PACAP increased adrenal catecholamine and Met5-enkephalin release, and CRF release was observed in the presence of ACTH.

Conclusions:

• PACAP exerts potent steroidogenic and vasodilator effects on the adrenal gland in conscious calves.
• PACAP modulates the release of catecholamines, enkephalins, and CRF from the adrenal medulla.
• These findings support PACAP's role as a potential neuromodulator in the bovine adrenal gland.