The effects of MK-212 [6-chloro-2-(1-piperazinyl)-pyrazine] (10, 20, and 40 mg, orally), a centrally acting serotonin (5-HT) receptor agonist and placebo, on serum cortisol, prolactin, and growth hormone levels were studied in eight healthy men over 3-hr. MK-212 produced a dose-related increase in