Serotonergic regulation of adrenocortical function

Serotonin (5-HT) plays a pivotal role in the regulation of the hypothalamo-pituitary-adrenal axis. In particular, 5-HT is involved in the stimulation of ACTH secretion during stress. Recent data indicate that, at the adrenal level, 5-HT acts as a local regulator of corticosteroid secretion. The presence of 5-HT in the adrenal gland has been demonstrated immunohistochemically and biochemically in various species including frog, mouse, rat and human. In the mouse, 5-HT has been detected in nerve fibers while, in the frog and rat, 5-HT appears to be sequestered in chromaffin cells. In man, 5-HT is stored in perivascular mast cells. In vivo and in vitro studies have shown that 5-HT stimulates mineralo- and glucocorticoid secretion from adrenal cells. In rat, the type of receptor involved in the corticotropic effect of 5-HT is still controversial. In the frog and the human, the effect of 5-HT on the adrenal cortex is mediated through a 5-HT4 receptor subtype positively coupled to adenylyl cyclase and calcium influx. Clinical studies indicate that 5-HT4 receptor agonists stimulate aldosterone secretion in healthy volunteers and in patients with aldosterone disorders. The 5-HT4 receptor agonist cisapride and angiotensin II exert additive effects on aldosterone secretion. In contrast, cisapride has no influence on ACTH-induced aldosterone release. Collectively, these findings suggest that intra-adrenal 5-HT stimulates the secretory activity of adrenocortical cells through a paracrine mode of communication involving a 5-HT4 receptor type. Serotonergic control of corticosteroid production may be involved in the physiological control of the activity of the adrenal cortex, in particular during inflammatory stress. 5-HT may also be implicated in the pathophysiology of aldosterone disorders.