Male Reproductive Tract

Seminal Plug Expulsion Induced by Electrical Stimulation of the Intermesenteric Nerve in Anesthetized Rats

Abstract
Synchronized activation of autonomic and somatic divisions of the nervous system respectively destined to the seminal tract including the bladder neck and the pelvi-perineal striated musculature is necessary for anterograde ejaculation. We aimed at investigating the role of intermesenteric nerves (IMN) in ejaculation in anesthetized rats. Electrical stimulation of intact IMN (IMN ES), and distal and proximal stump of the sectioned IMN was tested in isofluraneanesthetized male rats. ES of intact IMN was also applied to rats with acute spinal transection at the T8 level. The effects of IMN ES on emission and expulsion phases of ejaculation were evaluated by measuring seminal vesicle pressure (SVP) and bulbospongiosus (BS) muscle contractions, respectively. IMN ES could induce SVP increase and rhythmic contractions of BS muscle concomitantly with expulsion of seminal plug. When compared to intact IMN ES, the occurrence of ejaculation and rhythmic BS muscle contractions, but not SVP increase, were reduced in response to ES of the distal stump of the sectioned IMN. In comparison to intact IMN ES, the occurrence of ejaculation and rhythmic BS muscle contractions were not significantly modified, whereas increase in SVP was diminished when proximal stump of the sectioned IMN was stimulated. Spinalization abolished ejaculation and rhythmic BS muscle contraction, but did not impair SVP increase. It is concluded that both afferents conveyed by IMN and relaying supraspinally and efferents of IMN are involved in IMN ES-induced ejaculation. We propose that the IMN ES paradigm may be used to investigate physiological and pharmacological aspects of ejaculation.

Key words: Central Nervous System • Male sexual function • Seminal vesicles