Electromyographic study of ejaculatory mechanism

Abstract

Cavernosus muscle (CM), seminal vesicle (SV) and vasal ampullary (VA) contractions at ejaculation are said to be reflex mechanisms (ejaculatory reflex), which have been scarcely dealt with in the literature. We investigated the hypothesis that contraction of the CMs, SVs and VA at ejaculation is a reflex action. The electromyographic (EMG) activity of CM, SV and VA during ejaculation was recorded in 28 healthy men. The test was repeated after separate anaesthetization of the glans penis (GP), CMs, SVs, and VA in the pre-ejaculatory period. Latent ejaculatory time (LET) was calculated. CMs showed no EMG activity until rigid erection phase was reached. SVs and VA exhibited resting EMG activity which increased gradually with different stages of erection. At ejaculation, CMs, SVs and VA showed two to four intermittent contractions. The mean LET was 1.3 +/- 0.2 sec. GP anaesthetization led to the disappearance of CM, SV and VA EMG activity at ejaculation, while bland gel did not affect EMG activity. CMs, SVs and VA when anaesthetized in the pre-ejaculatory period exhibited no EMG activity at ejaculation, while saline did not affect EMG activity. Increased EMG activity of CM, SV and VA apparently denotes increase in their contractile activity. CM, SV and VA contraction on GP stimulation and ejaculation are assumed to be reflex actions and are mediated through the 'glans-cavernosovesicular reflex' (GCVR) which presumably represents the ejaculatory reflex. Changes in LET or evoked response would indicate a defect in the reflex pathway. The GCVR might act as an investigative tool in diagnosing erectile dysfunction, provided further studies are performed in this respect.

Characterization of bulbospongiosus muscle reflexes activated by urethral distension in male rats

“…This pattern of BSM activity is similar to that recorded during ejaculation in conscious, behaving rats and was termed the urethrogenital reflex (UGR). The BSM rhythmic contractions recorded during the UGR in rats is also similar to the BSM activity in men during ejaculation (4,5,43). In addition, the BSM activity in both men and rats, involves a spinal reflex that can be triggered by stimulation of penile afferent fibers of the dorsal nerve of the penis (18,23,46).…”

“…In addition, the BSM activity in both men and rats, involves a spinal reflex that can be triggered by stimulation of penile afferent fibers of the dorsal nerve of the penis (18,23,46). This reflex is thought to mimic the expulsion phase of ejaculation, since it is characterized by rhythmic contractions of the perineal muscles, which is necessary to expel seminal fluids (11,18,21,24,32,40,43,44). Therefore, the UGR is considered a surrogate for the peripheral and spinal components of somatic and autonomic reflexes that control ejaculation and has been used to determine the anatomical, physiological, and pharmacological characteristics of ejaculatory-like reflexes (ELR).…”

“…This reflex is thought to mimic the expulsion phase of ejaculation, since it is characterized by rhythmic contractions of the perineal muscles, which is necessary to expel seminal fluids (11,18,21,24,32,40,43,44). Therefore, the UGR is considered a surrogate for the peripheral and spinal components of somatic and autonomic reflexes that control ejaculation and has been used to determine the anatomical, physiological, and pharmacological characteristics of ejaculatory-like reflexes (ELR).Both penile and urethral stimulation (distension and/or pressure) are considered to provide ejaculatory sensory input in humans and rats (9,32,41,43,44). The sensory branch of the pudendal nerve (SbPN) carries both penile and urethral primary afferent fibers, while the pelvic nerve (PelN) and the hypogastric nerve (HgN) carry urethral primary afferent fibers (7,13,16,17,27).…”

“…Both penile and urethral stimulation (distension and/or pressure) are considered to provide ejaculatory sensory input in humans and rats (9,32,41,43,44). The sensory branch of the pudendal nerve (SbPN) carries both penile and urethral primary afferent fibers, while the pelvic nerve (PelN) and the hypogastric nerve (HgN) carry urethral primary afferent fibers (7,13,16,17,27).…”

“…During the emission phase, autonomic nerves (pelvic and hypogastric) regulate secretion of seminal fluids into the urethra. Expulsion of the seminal fluids is thought to occur in response to urethral afferent activation due to the presence of seminal fluids in the urethra (via stretch or chemoreceptors) and penile afferent activation due to mechanical stimulation of the penis (via cutaneous mechanoreceptors) and is characterized by rhythmic contractions of striated perineal muscles, primarily the bulbospongiosus muscle (BSM) (2,14,21,42,43,56). In acutely spinalized (T8 -T10), urethane-anesthetized rats, clamping the tip of the penis, while infusing fluid into the urethra, produces repeated, phasic contractions of the BSM (11,30,32).…”