Endocrine effects of 5-methoxytryptoline, 5-hydroxytryptoline and tryptoline, putative modulators of rat serotonergic system.

The effects of tryptolines (TH beta Cs), putative endogenous compounds acting on the serotonergic function, have been studied on endocrine parameters in rats. In particular, graded doses of 5-methoxytryptoline (5-MeOT), 5-hydroxytryptoline (5-OHT) and tryptoline (Tp) were ip or iv administered to the animals and the circulating titers of prolactin (PRL), growth hormone (GH) and luteinizing hormone (LH) were assayed either at 20 min or at various times after the injection of the compounds. The data herein reported show that TH beta Cs exert endocrine effects, at least in a pharmacological condition. However, the three compounds unequally affect anterior pituitary function. In fact, while 5-MeOT, 5-OHT and Tp all enhance plasma PRL concentrations in a quick, short lasting and dose-related manner, 5-MeOT and Tp induce also decreases of serum LH levels in ovariectomized rats, and 5-MeOT only is able to diminish plasma GH titers. These findings underline an endocrine effect for TH beta Cs in pharmacological conditions and may suggest a functional role for these compounds in the control of anterior pituitary function.