Food ingestion stimulates cortisol secretion in man, but the mechanism of this effect is unknown. We have investigated the possible role of adrenoceptors in the mediation of this effect. Six normal males were given continuous 3 h i.v. infusions of normal saline, methoxamine (alpha-1 adrenoceptor agonist) and thymoxamine (alpha-1 adrenoceptor antagonist). Methoxamine enhanced and thymoxamine attenuated the ACTH and cortisol responses to a standard meal given 60 min after commencement of the infusion. The drugs had no effect on nutrient absorption. Four patients with recent onset of pituitary ACTH deficiency and normally responsive adrenal glands showed no ACTH or cortisol rises after the standard meal, demonstrating that postprandial cortisol secretion is mediated by pituitary rather than gut ACTH. Our previous investigations have demonstrated that alpha-1 adrenoceptors stimulate pituitary ACTH secretion in man by an action within the blood brain barrier. We therefore conclude that postprandial cortisol secretion is mediated by central stimulant alpha-1 adrenoceptors modulating pituitary ACTH secretion.

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