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Mechanism of ejection during ejaculation: identification of a urethrocavernosus reflex
1Department of Surgery and Experimental Research, Cairo University, Egypt. shafisci@link.com.eg
Archives of Andrology
|February 26, 2000
Summary
The bulbocavernosus muscle (BCM) contracts reflexively in response to bulbous urethral distension, likely via the urethrocavernosus reflex, aiding semen propulsion during ejaculation. This reflex is crucial for understanding ejaculatory disorders.
Area of Science:
- Urology
- Neuroscience
- Physiology
Background:
- Ejaculation involves two reflexes: glans-vasal (emission) and urethromuscular (ejection).
- The bulbocavernosus muscle (BCM) plays a key role in semen expulsion.
- The precise mechanism of BCM contraction during ejaculation requires further elucidation.
Purpose of the Study:
- To investigate the mechanism of bulbocavernosus muscle (BCM) contraction in response to urethral distension.
- To determine the reflex pathway involved in BCM activation during ejaculation.
- To assess the threshold volume for BCM response to urethral distension.
Main Methods:
- 14 healthy males participated.
- A balloon-tipped catheter was used to distend the urethra at various points (prostatic, membranous, bulbous, pendulous).
- Electromyography (EMG) recorded BCM activity, and response latency was measured.
Main Results:
- Bulbous urethral distension, starting at 0.5 mL, significantly increased BCM EMG activity.
- BCM response latency was consistently around 10 ms.
- No BCM response was observed with distension of other urethral segments or with anesthetized tissues.
Conclusions:
- Bulbocavernosus muscle contraction is a reflex response to bulbous urethral distension, likely mediated by the urethrocavernosus reflex.
- A minimum distension volume is necessary to trigger BCM contraction.
- The urethrocavernosus reflex should be considered in the andrologic evaluation of ejaculatory dysfunction.