Chronic stress reduced GH response to the serotonin agonist 5‐methoxy‐n, n‐dimethyltriptamine but did not alter pituitary–adrenal, prolactin or TSH responses in the rat

The present work investigates the effect of a chronic stress model in which several acute stressors were applied on a random basis on pituitary–adrenal, prolactin, growth hormone (GH) and thyroid—stimulating hormone (TSH) responses to the serotonin agonist 5‐methoxy‐N, N‐dimethyltryptamine (MeODMT) administered peripherally. The drug stimulates pituitary–adrenal, prolactin and GH secretion at the two doses tested. Its effect on serum TSH was stimulatory at the lower dose but had no effect at the higher dose. Previous chronic stress did not alter pituitary‐adrenal, prolactin and TSH responses to the drug. In contrast, reduced GH response to MeODMT was observed in chronically stressed rats, suggesting that subsensitivity to serotonin was present after chronic stress. The present results indicate that serotonergic pathways controlling anterior pituitary hormone secretion respond heterogeneously to chronic stress. Copyright © 1990 John Wiley & Sons, Ltd