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

Abstract

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. K E Y W O R D Sbulbospongiosus, cystometrograms, intraurethral, pubococcygeus, stress urinary incontinence

Targeted neuromodulation of pelvic floor nerves in aging and multiparous rabbits improves continence

“…An additional limitation to the study is the anatomical difference between the rabbit and human urogenital system. The rat model has been commonly studied to evaluate bladder and pelvic floor function 40 ; in this study, the rabbit was chosen due to the larger pelvic floor muscles, and anatomical and functional characterization of the multiparity and aging effects that includes neural dysfunction in nerve conduction, muscle damage, and urethral and bladder abnormalities 22 .…”

“…They were pregnant and lactating for twenty days when pups were weaned, as it occurs in normal, natural conditions. On the day of the fourth delivery, neonate pups were euthanized to avoid lactation and to allow multiparous rabbits to set their hormonal conditions similar to nulliparous animals, as reported for serum estradiol levels 22 , 45 . The average litter size in multiparous animals was 6 pups (5, 7, 7, 6 for each animal per delivery, respectively).…”

“…A balloon-catheter (1.6 mm and 1.2 mm outer and inner diameters, respectively) was introduced into the urethra and inflated using warm saline, reaching a 4.5 ± 0.70 mm diameter partially obstructing the urine flow. The balloon catheter was connected to a pressure transducer (Grass PT 300) which was connected to a signal acquisition system (Grass 7P1B DC amplifier) to record the urethral pressure (P ura ), as previously described 22 . Urodynamic data was visualized and quantified in the PolyView recorder (ver.…”

“…Normal saline solution (0.9% NaCl) was infused at a constant rate of 0.8 mL/min at body temperature (37 °C) into the bladder. The P ves and P ura baselines were simultaneously recorded in triplicate during bladder filling and voiding phases following the procedures described in previous studies 15 , 22 , 51 . Briefly, the maximum urethral pressure ( max P ura ) during voiding, the total voided volume defined as the volume (mL) expelled through the urogenital meatus during voiding, and voiding efficiency as the percentage of total voided volume divided by the total infused saline solution at the time of micturition were calculated.…”

“…in contrast with rats, rabbits have no vestigial pelvic floor muscles) [13][14][15][16] . In these animals, multiparity and aging result in PFM weakness, desynchronized muscle contraction patterns, and low urethral pressure and bladder efficacy [17][18][19][20][21][22] . Recently, we reported that nerve conduction in pelvic floor nerves is compromised in multiparous and aging rabbits, as evoked action potentials are reduced approximately 10-12% in young (12-18 months) and mid-age (3-4 years) multiparous animals compared to young nulliparous controls 18 .…”