Muscarinic adrenal responses to acetylcholine in conscious calves.

Abstract

SUMMARY1. Adrenal responses to intra-aortic infusions of acetylcholine (4-5 nmol min-' kg-' for 10 min) have been investigated in hypophysectomized conscious calves given exogenous adrenocorticotrophic hormone (ACTH) (2 ng min-' kg-' i.v.) in the presence and absence of hexamethonium.2. Acetylcholine produced a significant increase in adrenal cortisol output and plasma cortisol concentration. In the absence of nicotinic blockade with hexamethonium this was apparently accounted for by an increase in adrenal ACTH presentation secondary to increased adrenal blood flow. However, administration of hexamethonium revealed a direct steroidogenic action of acetylcholine in the presence of exogenous ACTH 3. Adrenal medullary responses to acetylcholine, including the release of catecholamines, enkephalins and corticotrophin-releasing factor (CRF), were not significantly reduced by nicotinic blockade.4. It is concluded that both adrenal medullary and cortical responses to intraaortic infusions of acetylcholine at a low dose are mediated mainly by muscarinic receptors, as it has previously been shown that they are substantially reduced in the presence of atropine.

Mechanisms for establishment of GABA signaling in adrenal medullary chromaffin cells

“…This species difference in expression incidence and amount of GABA A receptors in AMC cells may be ascribed to glucocorticoids produced in adrenal cortical cells. The major glucocorticoid in guinea‐pig (Malinowska & Nathanielsz, 1974) and bovine adrenal cortical cells (Bloom et al., 1977; Jones & Edwards, 1991) is cortisol, whereas that in mice (Taves et al., 2015) and rats (Bernardi et al., 1998; Hashimoto et al., 1989; Zoccal et al., 2007) is corticosterone. Hamster adrenal cortical cells are a dual secretor, mainly secreting corticosterone under basal and cortisol under stressful conditions (Ottenweller et al., 1985).…”

“…The fact that GABA A receptors already develop at birth raises the possibility that the development of GABA A receptors in AMC cells (Malinowska & Nathanielsz, 1974) and cattle (Bloom et al, 1977;Jones & Edwards, 1991) is cortisol, whereas that in mice (Taves et al, 2015) and rats (Bernardi et al, 1998;Hashimoto et al, 1989;Zoccal et al, 2007) is corticosterone. Because the potency of corticosterone in lowering serum Ca 2+ in rats was reported to be one-eighth that of cortisol (Mahgoub et al, 1997), the low glucocorticoid activity of corticosterone might explain low expression levels of GABA A receptors in rodent AMC cells (Inoue et al, 2013).…”

Regulation of Adrenal Function in the Conscious Calf

“…In addition to the well documented effects on the medulla, which are mediated by acetylcholine acting on nicotinic receptors, it has been established in the conscious calf model that adrenal medullary and cortical responses to low doses of acetylcholine infused intra-aortically (4.5 nmol mm-1 kg-1) are mediated via muscarinic receptors (110,111). These include the release of catecholamines, enkephalins and CRH, together with cortisol and aldosterone.…”

Adrenal cortical and medullary responses to acetylcholine and vasoactive intestinal peptide in conscious calves.

“…The output of cortisol from the adrenal gland in response to adrenocorticotrophic hormone (ACTH) is potentiated by intra-aortic infusions of small amounts of both acetylcholine and of vasoactive intestinal peptide (VIP) in the conscious calf (Bloom, Edwards & Jones, 1987;Jones, Edwards & Bloom, 1991). The response to acetylcholine is attributable to activation of muscarinic receptors (Jones & Edwards, 1992). Release of VIP is thought to be implicated in the potentiation of the steroidogenic response to ACTH during splanchnic nerve stimulation, both in the conscious calf (Bloom et al 1987) and the perfused adrenal gland of the pig, MS 1756 A. V. EDWARDS AND C. T. JONES when the nerve supply is preserved (Erhart-Bornstein, Bornstein, Scherbaum, Pfeiffer & Holst, 1991).…”