Pelvic floor muscles and sphincters during erection and ejaculation

Area of Science:

• Veterinary Urology
• Canine Reproductive Physiology
• Pelvic Floor Mechanics

Background:

• The pelvic floor, comprising muscles like the puborectalis (PR) and levator ani (LA), and sphincters such as the external anal sphincter (EAS) and external urethral sphincter (EUS), plays a crucial role in urinary and fecal continence, as well as sexual function.
• Understanding the dynamic interplay of these structures during sexual events like erection and ejaculation is vital for diagnosing and treating related functional disorders in animals.

Purpose of the Study:

• To investigate the electromyographic (EMG) activity of the pelvic floor muscles (PR, LA) and sphincters (EAS, EUS) in dogs during electroejaculation (EE)-induced erection and ejaculation.
• To elucidate the specific roles of these muscles and sphincters in the physiological processes of erection and ejaculation, including potential contributions to prostatic secretion expulsion and genital fluid propulsion.

Main Methods:

• Electromyographic (EMG) activity of the puborectalis (PR), levator ani (LA), external anal sphincter (EAS), and external urethral sphincter (EUS) was recorded in 12 anesthetized mongrel dogs.
• Electroejaculation (EE) was employed to induce erection and ejaculation, with varying voltage and current levels applied until ejaculation occurred.
• Penile tumescence, rigidity, and changes in EMG activity of the studied muscles and sphincters were monitored and correlated with EE parameters.

Main Results:

• Penile tumescence and rigidity were observed concurrently with increased EMG activity in the PR, LA, EAS, and EUS.
• EMG activity and penile rigidity progressively increased with rising voltage and current during EE, culminating in ejaculation at a mean voltage of 11.1 ± 1.2 V and current of 122.4 ± 14.4 mA.
• Specific muscle actions were inferred: PR activity may facilitate prostatic secretion expulsion, LA contraction might aid prostate elevation and urethral straightening, and EAS/EUS contractions likely prevent leakage and assist in fluid ejection during ejaculation.

Conclusions:

• Pelvic floor muscles and sphincters exhibit significant, coordinated activity during canine erection and ejaculation.
• The observed contractions suggest functional roles in supporting sexual function, including the potential expulsion of prostatic secretions and the rhythmic propulsion of genital fluids.
• These findings provide insights into the neuromuscular control of canine reproduction and may inform the understanding of related urogenital conditions.