Hypothyroidism impairs somatovisceral reflexes involved in micturition of female rabbits

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.

The Expression of Hormone Receptors as a Gateway toward Understanding Endocrine Actions in Female Pelvic Floor Muscles

OBJECTIVE

To provide an overview of the hormone actions and receptors expressed in the female pelvic floor muscles, relevant for understanding the pelvic floor disorders.

METHODS

We performed a literature review focused on the expression of hormone receptors mainly in the pelvic floor muscles of women and female rats and rabbits.

RESULTS

The impairment of the pelvic floor muscles can lead to the onset of pelvic floor dysfunctions, including stress urinary incontinence in women. Hormone milieu is associated with the structure and function alterations of pelvic floor muscles, a notion supported by the fact that these muscles express different hormone receptors. Nuclear receptors, such as steroid receptors, are up till now the most investigated. The present review accounts for the limited studies conducted to elucidate the expression of hormone receptors in pelvic floor muscles in females.

CONCLUSION

Hormone receptor expression is the cornerstone in some hormone-based therapies, which require further detailed studies on the distribution of receptors in particular pelvic floor muscles, as well as their association with muscle effectors, involved in the alterations relevant for understanding pelvic floor disorders.

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.