Evidence for Peripheral Effect of Serotonin on Ejaculatory Response

Paick, Jae Seung; Park, Dal Woo; Son, Hwancheol; Lee, Sung Ho; Kim, Soo Woong

Abstract

PURPOSE: Although serotonin (5-HT) has been implicated in central control of sexual desire, erection and ejaculation, its peripheral effect has been poorly studied. Here, we investigated the peripheral effects of 5-HT on ejaculation using in vivo and in vitro experiments.
MATERIALS AND METHODS
Male Sprague-Dawley rats (weighed 250-300 g) were injected intravenously with serotonergic agents (serotonin, fluoxetine, clomipramine) at various concentrations 20 min before electrical nerve stimulation of the hypogastric nerve. Intraluminal pressure of seminal vesicle and vas deferens was measured on each side in the same animal and compared. Total RNA was isolated from brain, seminal vesicle and vas deferens. Expressions of mRNAs for 5-HT(1A), 5-HT(1B) and 5-HT(2C) receptors, which have been suggested for ejaculatory responses, were examined using semi-quantitative reverse-transcriptase polymerase chain reaction.
RESULTS
All serotonergic agents caused dose-dependent inhibition of elevation in intraluminal pressure of the seminal vesicle. Vasal pressure responses were effectively inhibited by clomipramine and serotonin (clomipramine>serotonin), whereas no effect was seen by fluoxetine. There was no significant difference in relative expression levels of 5-HT(1A) receptor mRNAs between the seminal vesicle and vas deferens. However, the expression levels of 5-HT(1B) and 5-HT(2C) receptors mRNAs were lower in the vas deferens when comparing to those in the seminal vesicle.
CONCLUSIONS
These results of in vivo and in vitro experiments provide evidence for the peripheral role of 5-HT in regulating ejaculatory response of male rats. Regional differences in distributions of 5-HT receptor subtypes between seminal vesicle and vas may contribute to the different response to serotonergic agents in these organs.