PHYSIOLOGICAL-ROLE OF THE OPIOID-CHOLINERGIC INTERACTION IN GROWTH-HORMONE NEUROREGULATION - EFFECT OF SEX AND FOOD-INTAKE

Studies performed in animals and humans have suggested a functional in teraction between opioid and cholinergic systems in the control of gro wth hormone (GH) secretion. Moreover, the sex-dependent modulation of GH secretion in humans is well established, To investigate the role of sex and food intake in the regulation of the reciprocal influences of opioids and acetylcholine in the modulation of GH secretion, we studi ed the GH response to pyridostigmine (PYR) alone and during a naloxone (NAL) infusion in a group of normal men and women before a meal (at 1 :00 PM) and postprandially. In women, the response of GH to PYR alone before the meal was significantly lower than in the men (area under th e curve [AUG], mean +/- SEM, 320,18 +/- 87.16 v 1,031.06 +/- 333.21 mu g/L/90 min, P<.01), Before the meal, NAL completely abolished the res ponse of GH to PYR in men (AUG, 1,031.06 +/- 333.21 v 16.50 +/- 7.50 m u g/L/90 min, P <,01), whereas infusion of NAL did not significantly m odify the GH response to PYR in women. Consumption of the meal signifi cantly decreased PYR-induced GH release in both women (AUC, 21.75 +/- 12.75 v 320.18 +/- 87.16 mu g/L/90 min, P <.05) and men (AUG, 45.75 +/ - 18.75 v 1,031.06 +/- 333.21 mu g/L/90 min, P<.01). Conversely, food intake did not change the effects of NAL infusion on the GH response t o PYR either in women or in men, We conclude that the sex-dependent op ioid modulation of PYR-induced GH secretion is observed before a meal but not in the postprandial state, Food intake may be hypothesized to influence the cholinergic regulation of GH secretion and the sex-depen dent opioid modulation of central cholinergic tone. Copyright (C) 1997 by W,B. Saunders Company.