Serotoninergic control of prolactin secretion in prepubertal male rats

The role of the serotoninergic system in the control of prolactin (PRL) secretion has been studied in prepubertal male rats. Serum PRL concentration was measured in 16-day-old male rats at different times after the administration of 5-hydroxytryptophan (5-HTP), a precursor of serotonin (5-HT) synthesis, alone or in combination with fluoxetine, a specific inhibitor of 5-HT uptake; DL-p-parachlorophenylalanine (PCPA), an inhibitor of 5-HT synthesis; and 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT), a selective agonist of 5-HT1A receptors. Also, serum PRL concentration and pituitary content were measured after 5-HTP administration in castrated males implanted with silastic capsules containing testosterone or 5 alpha-androstane-3 alpha,17 beta-diol (alpha-diol). We found that: the reduction in serotoninergic activity after PCPA administration did not modify serum PRL concentrations; the stimulatory effect of 5-HTP on PRL secretion was not observed before day 16; the effects of 5-HTP or 5-HTP and fluoxetine were similar in intact and orchidectomized males; a significant increase in PRL secretion took place after 8-OH-DPAT administration; the duration of the stimulatory effect of 5-HTP increased after alpha-diol treatment; and pituitary PRL content increased after 5-HTP injection in intact males and decreased in castrated males treated with testosterone or alpha-diol.(ABSTRACT TRUNCATED AT 250 WORDS)