Neuro-endocrine effects of isotheoline

Experiments are carried out to study the effect of isotheoline (IST) on the secretion of prolactin (PRL), somatotrophic hormone (STH) and testosterone, using cats and Wistar albino rats of both sexes. PRL, STH and testosterone using cats and wistar albino rats of both sexes. PRL, STH and testosterone were determined radioimmunologically at the 10th, 60th and 120th min after the administration of IST in doses of 0.5 to 5 mg/kg. Comparative experiments were carried out with bromocryptine and glaucine--1 mg/kg i.p., as well as experiments involving the administration of IST on the background of the dopaminergic antagonists haloperidol and pymoside--1 mg/kg i.p. The results obtained show that in doses not exceeding 1 mg/ks IST increases the plasma level of testosterone and, similar to bromocryptine, reduces the plasma level of PRL and increases that of STH. These effects are less pronounced for the 5 mg/kg dose and they are antagonized by the dopaminergic antagonists used. It is assumed that IST, similar to bromocryptine, achieves the described effects through selective stimulation of the D2 dopaminergic receptors involved in neuro-endocrine mechanisms responsible for the control and release of the hormones studied.