The cotton pellet technique was used to evaluate the effect of 5-HT and certain related compounds on granuloma formation in the rat. 5-HT (10 mg/kg) significantly decreased granuloma formation, significantly increased adrenal weight, and significantly decreased thymus weight in normal rats, and significantly decreased granuloma formation and thymus weight in sham-operated rats. On the other hand, 5-HT (10 mg/kg) significantly increased granuloma weight in adrenalectomized rats.
Methysergide (1 mg/kg) blocked the inhibitory effect of 5-HT on granuloma formation as well as the changes in weight of adrenal and thymus glands.
5-HIAA (11 mg/kg) and 5-HTP (13 mg/kg) failed to alter granuloma formation.