EFFECTS OF RITANSERIN, A SPECIFIC SEROTONIN-S-2 RECEPTOR ANTAGONIST, ON THE RELEASE OF ANTERIOR-PITUITARY HORMONES DURING INSULIN-INDUCED HYPOGLYCEMIA IN NORMAL HUMANS

The role of serotonin in the insulin hypoglycemia (IH) stimulated secr etion of prolactin (PRL), growth hormone (GH), adrenocorticotropin (AC TH) and cortisol (F) was studied in a group of 12 normal subjects duri ng the control period after placebo and a consecutive six-day treatmen t with 20 mg ritanserin (RIT) per day, RIT failed to affect the baseli ne levels of ail the four hormones as well as the PRL response to IH ( p>0.5). The serum GH response to IH was moderately diminished after RI T, the reduction of integrated trapezoidal area under hormone curves ( nAUC) being 50.7% +/- 6.9% (p<0.005). Furthermore, RIT was found to sl ightly decrease the plasma ACTH response to IH, the reduction of nAUC being 36.3% +/- 2.6% (p<0.005). Decrease in the corresponding plasma F response to IH was accompanied by 29.1% +/- 2.4% reduction of nAUC (p <0.005). According to our results, serotonin-S-2 receptors appeared to be moderately involved in IH-induced release of GH, but slightly in t hat of ACTH, leaving unaffected that of PRL.