Stimulatory Role for Brain Serotoninergic System on Prolactin Secretion in the Male Rat 1

Abstract

Summary

Systemic administration of parachlorophenylalanine (PCPA, 100 mg/ kg sc on alternate days x two times), a blocker of serotonin (5-HT) synthesis, considerably decreased brain 5-HT and plasma prolactin (PRL) levels in young male rats. Intraventricular (IVT) administration of 5,7-dihydroxytryptamine (5,7-DHT, 200 μg/20 μl), a neurotoxic drug which destroys 5-HT nerve terminals, induced, 3, 12, and 30 days after treatment, a marked depletion of brain 5-HT and 5-hydroxyindoleacetic acid (5-HIAA) and considerably reduced plasma PRL levels at each time interval. Feeding of rats for up to 4 days with a tryptophan (TP)-deficient diet, caused a depletion of brain 5-HT and 5-HIAA contents and did not modify plasma PRL levels. Addition of TP (2 g/kg of diet) to the TP-deficient diet resulted in increased brain 5-HT and 5-HIAA contents and significantly increased PRL levels. These data provide evidence for the role of the 5-HT system in the maintenance of tonic PRL secretion.

We are grateful for the technical assistance of Miss Tecla Ciapparelli and Mr. Giuseppe Tavasci, and to Miss Delia Deriu for skillful secretarial help. Dr. H. G. Baumgarten kindly supplied 5,7-DHT. The reagents for the rat PRL radioimmunoassay were a gift of the Rat Pituitary Hormone Distribution Program of the National Institute of Arthritis, Metabolism, and Digestive Diseases.