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 (IMNs) in ejaculation in anesthetized rats. Electrical stimulation of intact IMNs and distal and proximal stumps of the sectioned IMN were tested in isoflurane-anesthetized male rats. Electrical stimulation of the intact IMN was also applied to rats with acute spinal transection at the T8 level. The effects of IMN electrical stimulation on emission and expulsion phases of ejaculation were evaluated by measuring seminal vesicle pressure (SVP) and bulbospongiosus (BS) muscle contractions, respectively. IMN electrical stimulation could induce SVP increase and rhythmic contractions of BS muscle concomitantly with expulsion of the seminal plug. When compared with intact IMN electrical stimulation, the occurrence of ejaculation and rhythmic BS muscle contractions, but not SVP increase, was reduced in response to electrical stimulation of the distal stump of the sectioned IMN. In comparison to intact IMN electrical stimulation, the occurrence of ejaculation and rhythmic BS muscle contractions was not significantly modified, whereas the increase in SVP was diminished when the 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 electrical stimulation-induced ejaculation. We propose that the IMN electrical stimulation paradigm can be used to investigate physiological and pharmacologic aspects of ejaculation.

Thoracolumbar epidural stimulation effects on bladder and bowel function in uninjured and chronic transected anesthetized rats

“…Seminal fluid contains seminal vesicle material that hardens when exposed to prostatic enzymes 54 – 57 . To prevent occlusion of the urethra, the seminal vesicles were ligated (4-0 silk suture).…”

Bladder and bowel responses to lumbosacral epidural stimulation in uninjured and transected anesthetized rats

“…Additionally, the more specific Micro-Leads electrode array has not been tested in males and therefore it is not clear if plug release could be avoided with more localized targeted stimulation. Seminal plugs contain material released from the seminal vesicles 49 which is also served by neural circuitries that includes the L5-S1 cord, the pelvic nerves as well as the hypogastric nerves [50][51][52] . Importantly, scES during mapping was applied over a large area without specific targeting, which could have activated ejaculatory related circuitry leading to plug material found during post-mortem examination.…”

Experimental Models for the Study of Female and Male Sexual Function

“…The other end of the catheter is connected to a pressure transducer coupled with an amplifier and an analog‐to‐digital converter. The output is transformed to numeric data on a computer where the signals can be visualized and recorded [123].…”

“…To measure the intraluminal pressure, the vas is incised above the prostatic junction and a catheter is advanced into the lumen over ∼1 cm in the direction of the urethra. With the catheter in situ, measurement of the pressure changes can be performed similar to the above‐mentioned seminal vesicle pressure estimation [123].…”