Lumbosacral ventral root avulsion alters reflex activation of bladder, urethra, and perineal muscles during micturition in female rabbits.

AIM: To determine the effect of the lumbosacral ventral root avulsion (VRA) on the reflex activation of bladder, urethra, and activation of perineal muscles during micturition in female rabbits. METHODS: We allocated 14 virgin female rabbits to evaluate, first, the gross anatomy of lumbosacral spinal cord root (n = 5) and, second, to determine the effect of VRA on perineal muscles during micturition (n = 9). We recorded cystometrograms, urethral pressure, and electromyograms of the bulbospongiosus (Bsm) and ischiocavernosus (Ism) muscles before and after the L6-S2 VRA. Standard variables were measured from each recording and analyzed to identify significant differences (P < .05). RESULTS: We found that the L6-S2 VRA affected directly the bladder and urethral function and reduced the duration and the frequency of the bursting of Ism and Bsm muscles during voiding. The Ism and Bsm showed a phasic activation, of different frequencies, during the voiding phase and the L6-S2 VRA inhibited the co-contraction of the Ism and Bsm-bladder-urethra. CONCLUSIONS: The Ism and Bsm are activated at different frequencies to trigger the voiding phase. The L6-S2 VRA affected the activity pattern of both perineal muscles. These modifications affected the bladder and urethra function. It is possible that the restoration of the activation frequency of perineal muscles contributed for an efficient bladder contraction.

Bladder and urethral dysfunction in multiparous and mature rabbits correlates with abnormal activity of pubococcygeus and bulbospongiosus muscles.

AIMS: To evaluate the combined effect of age and multiparity on the micturition reflex, including pelvic floor muscle activation. METHODS: Young and mature nulliparous rabbits were compared to young and mature multiparas (n = 6 per group). Cystometrograms and urethral pressure (UP) were performed while simultaneously recording the electromyogram (EMG) activity of the pubococcygeus and bulbospongiosus muscles to establish their functional correlation to urological function. RESULTS: Multiparity and age significantly influence the bladder and UP affecting the voiding efficiency and intercontraction interval. Such interaction also reduced the UP threshold, timing, and duration. Other bladder and urethral variables were predominantly affected only by age. Urodynamic alterations correlated with abnormal patterns or absent EMG activity of the pubococcygeus and bulbospongiosus muscles. CONCLUSIONS: The present findings strongly suggest that multiparity and age affects specific pelvic floor muscle reflex activation during micturition, and may contribute to alterations in bladder and urethral function. This data broadens our understanding of the critical role of the appropriate activity of the individual pelvic floor muscles in micturition.

Multiparity modifies contractile properties of pelvic muscles affecting the genesis of vaginal pressure in rabbits.

AIMS: To characterize the contractile properties of the bulbospongiosus (Bsm), isquiocavernosus (Ism), and pubococcygeus muscles (Pcm), and their involvement in the genesis of vaginal pressure in nulliparous and multiparous rabbits. METHODS: Age-matched nulliparous and multiparous rabbits were used to record the isometric contractile responses of each muscle as well as the intravaginal pressure evoked by single square electrical pulses and stimulation trains of ascending frequency. To establish significant differences between groups, two-tail unpaired Student t tests were carried out. The linear correlation between intravaginal pressure and muscle contractile force was analyzed with Pearson correlation tests. For all cases, a P ≤ 0.05 was set as statistically significant. RESULTS: Multiparity decreased the contractile force of Bsm and Ism generated by high-frequency stimulation trains. The normalized force of the Pcm increased when evoked at 1, 4, and 10 Hz while this decreased at higher frequencies (20, 50, and 100 Hz). The contraction of both Bsm and Ism raised particularly the pressure on the perineal vagina while that of the Pcm increased the pressure in the pelvic vagina. Such a functional segregation is still present in multiparous rabbits albeit it was modified. CONCLUSIONS: Multiparity induces changes in the contractile responses of Bsm, Ism, and Pcm, which alterates the vaginal pressure.

Hypothyroidism impairs somatovisceral reflexes involved in micturition of female rabbits.

AIMS: To determine the impact of hypothyroidism on the bladder and urethral functions as well as in the activation of the pubococcygeous (Pcm) and bulbospongiosus (Bsm) during micturition. METHODS: Age-matched control and methimazole-induced hypothyroid female rabbits were used to simultaneously record cystometrograms, urethral pressure, and the reflex activation of Pcm and Bsm during the induced micturition. Urodynamic and urethral variables were measured. Activation or no activation of the Pcm and Bsm during the storage and voiding phases of micturition were categorized as 1 or 0. Significant differences (P ≤ 0.05) between control and hypothyroid groups were determined with unpaired Student-t or Mann-Whitney tests. RESULTS: One-month induced hypothyroidism increased the residual volume and threshold pressure while the opposite was true for the voided volume, maximal pressure, and voiding efficiency. Urethral pressure was also affected as supported by a notorious augmentation of the urethral resistance, among other changes in the rest of measured variables. Hypothyroidism also affected the reflex activation of the Pcm in the voiding phase of micturition. CONCLUSIONS: Our findings demonstrate hypothyroidism impairs the bladder and, urethral functions, and reflex activation of Pcm and Bsm affecting the micturition in female rabbits.

Anatomic and functional properties of bulboglandularis striated muscle support its contribution as sphincter in female rabbit micturition.

PURPOSE: To determine anatomic and functional properties of the bulboglandularis muscle (Bgm) for clarifying its role in micturition in female rabbits. MATERIAL AND METHODS: Virgin female rabbits were used to describe the gross anatomy and innervation of the Bgm, to determine the effect of the Bgm contraction on urethral pressure, and to evaluate the Bgm activity during the induced-micturition. Both electromyogram and cystometrogram activity were simultaneously recorded in urethane-anesthetized rabbits. Bladder function was assessed measuring standard urodynamic variables before and after blocking the Bgm activity for approaching its contribution to micturition. The relevance of the Bgm activation for micturition was approached applying lidocaine injections. RESULTS: The Bgm was composed of circularly oriented striated fibers enveloping distal urethra and pelvic vagina. Both the venous plexus and urethra were comprised by the Bgm contraction induced by electrical stimulation. The Bgm showed bursts of tonic activity at the storage phase of micturition that gradually decreased until turning off as the onset of the voiding phase. The voided volume, the voiding efficiency, the threshold pressure, and the maximal pressure were decreased after lidocaine injection. Contrastingly, the threshold volume, the residual volume, the voiding duration, and the urethral resistance at voiding were increased. CONCLUSIONS: Present anatomical and physiological findings support that the Bgm acts as a sphincter during micturition of female rabbits. Neurourol. Urodynam. 35:689-695, 2016. © 2015 Wiley Periodicals, Inc.

Estrogens influence differentially on the pelvic floor muscles activation at somatovisceral reflexes involved in micturition of rabbits.

OBJECTIVE: To determine the estrogen-dependency of the bladder and urethral function and the coordinated activation of pelvic floor muscles (PFM) during micturition. METHODS: We allocated age-matched female rabbits to control, 1-month ovariectomized (OVX), and OVX plus 2-week estradiol benzoate (EB) groups to record cystometry, urethral pressure, and electromyograms of bulbospongiosus (Bsm), and pubococcygeus muscles (Pcm) simultaneously. We also measured serum estradiol levels and myofiber cross-sectional area. We assessed urodynamic and urethral variables, categorized the Bsm-Pcm activation patterns at storage and voiding phases, and obtained the power spectrum density of muscle activation around the voiding phase. We investigated the influence of ovarian hormones, in general, and the contribution of estrogen, particularly on the functions of the bladder, urethra, and PFM. Statistical significance was set at P < 0.05. RESULTS: Ovarian hormones influence the bladder, urethral, and PFM functions. The urodynamics analyses indicated estrogens contribute to voiding duration and, to a lesser extent, to the time between bladder contractions. Urethral pressure at closure (maximal pressure-to-maximal urethral pressure ratio) improved partially (8%, P < 0.05) in the OVX plus 2-week estradiol benzoate compared with OVX, but urethral resistance increased (∼1.9-fold, P < 0.05) compared with control rabbits. Our findings support that Pcm activity at voiding is estrogen-sensitive, albeit EB administration reduced it at storage resume, which relates to high urethral resistance. CONCLUSIONS: Ovariectomy impairs bladder and urethral pressures and Bsm and Pcm activation at micturition in anesthetized rabbits. Estrogen administration partially reverts some of these effects and influences Pcm activation.