PURPOSE: To characterize the electromyographic activity of abdominal striated muscles during micturition in urethane-anesthetized female mice, and to quantitatively evaluate the contribution of abdominal responses to efficient voiding. METHODS: Cystometric and multichannel electromyographic recordings were integrated to enable a comprehensive evaluation during micturition in urethane-anesthetized female mice. Four major abdominal muscle domains were evaluated: the external oblique, internal oblique, and superior and inferior rectus abdominis. To further characterize the functionality of the abdominal muscles, pancuronium bromide (25 μg/mL or 50 μg/mL, abdominal surface) was applied as a blocking agent of neuromuscular junctions. RESULTS: We observed a robust activation of the abdominal muscles during voiding, with a consistent onset/offset concomitant with the bladder pressure threshold. Pancuronium was effective, in a dose-dependent fashion, for partial and complete blockage of abdominal activity. Electromyographic discharges during voiding were significantly inhibited by applying pancuronium. Decreased cystometric parameters were recorded, including the peak pressure, pressure threshold, intercontractile interval, and voiding duration, suggesting that the voiding efficiency was significantly compromised by abdominal muscle relaxation. CONCLUSIONS: The relevance of the abdominal striated musculature for micturition has remained a topic of debate in human physiology. Although the study was performed on anesthetized mice, these results support the existence of synergistic abdominal electromyographic activity facilitating voiding in anesthetized mice. Further, our study presents a rodent model that can be used for future investigations into micturition-related abdominal activity.
Abdominal Muscles* ; Animals ; Electromyography ; Female* ; Humans ; Lower Urinary Tract Symptoms ; Mice* ; Muscle, Striated ; Neuromuscular Junction ; Pancuronium ; Physiology ; Rectus Abdominis ; Relaxation ; Rodentia ; Urinary Bladder ; Urination*

Purpose: This study was conducted to evaluate the hypothesis that an enlarged prostate in old rats may lead to complications associated with voiding dysfunction involving ionotropic P2X2/3-type purinergic receptors Methods: Intact animals were divided into male young (MYR; 8–10 weeks old) and male old (MOR; 20 months old) rats. The animals underwent simultaneous detrusor electromyography (EMG) and suprapubic cystometry (CMG) under urethane anesthesia. Immunofluorescence techniques were used to evaluate prostatic autonomic innervation and P2X3R expression in bladder urothelial cells. The functional role of P2X3R was characterized by intramuscular application of AF-353, a selective P2X2/3R antagonist. Results: The prostate index significantly increased in MOR, suggestive of an enlarged prostate affecting micturition patterns. Significant EMG and CMG differences were found between MYR and MOR. Higher immunoreactivity for P2X2/3R in the urothelial layer and for prostatic neurofilaments was seen in MOR. Systemic inhibition of P2X2/3R had minimal effects on MYR responsiveness, but improved voiding function in MOR with a marked decrease of intravesical pressure and bladder contractile responses. Conclusions The data support the hypothesis that an enlarged prostate in MOR may contribute to voiding dysfunction involving activation of P2X2/3R, which enhances a prostate-bladder reflex. This reflex may increase bladder afferent transmission and activation of increased prostate innervation, leading to voiding dysfunction.

PURPOSE: To simultaneously monitor electrical discharges in various bladder regions and the external urethral sphincter (EUS) during voiding contractions, and to assess the functional role of myogenic modulation of the lower urinary tract (LUT) by ionotropic purinergic receptors containing the P2X3 subunit. METHODS: Female Sprague-Dawley rats were anesthetized with urethane, and implanted with a suprapubic catheter for open cystometry. Flexible microelectrodes were placed ventrally in the bladder dome, upper bladder, lower bladder, and bladder base, along with the middle section of the exposed EUS. Intravesical P2X3-containing receptors were blocked with AF-323, a specific P2X3-P2X2/3 receptor antagonist. A digital electrophysiology amplifier was used to record electrical and cystometric signals throughout the LUT. RESULTS: Electrical activity in the LUT started before effective voiding contractions. Bladder pressure and electrical waveforms showed consistent out-of-phase activity when compared with the recordings made at the EUS. This pattern was also observed during voiding contractions in the presence of AF-353, supporting the hypothesis that during bladder distension, activation of P2X3-containing receptors is required for voiding contractions. Furthermore, the inhibition of P2X3-containing receptors significantly decreased the amplitude of electrical signals in the urinary bladder, but not the base or EUS. CONCLUSIONS: Our results provide novel information about the regulation of the micturition process by P2X3-containing receptors located in the inner layers of the bladder.
Animals ; Catheters ; Electrophysiology ; Female* ; Humans ; Lower Urinary Tract Symptoms ; Microelectrodes ; Purinergic P2X Receptor Antagonists ; Rats* ; Rats, Sprague-Dawley ; Receptors, Purinergic ; Urethane ; Urethra ; Urinary Bladder* ; Urinary Tract ; Urination*