Changes in urethral smooth muscle and external urethral sphincter function with age in rats

Abstract

To confirm changes in urethral activity with age, both intravesical pressure and urethral perfusion pressure (UPP) were recorded and external urethral sphincter electromyography (EUS‐EMG) was performed. A total of 33 female Sprague Dawley rats aged 3 months (young rats), 12 months (middle‐aged rats), and 24 months (aged rats) were used. Bladder activity was evaluated using continuous cystometry. Urethral activity was evaluated by simultaneously recording intravesical pressure and UPP in isovolumetric conditions under urethane anesthesia in each group. Additionally, EUS‐EMG activity was monitored under the same conditions. In continuous cystometry, the amplitude of bladder contractions was not different among the three groups; nevertheless, residual urine volume was significantly increased in middle‐aged and aged rats, as compared in young rats. With respect to UPP, the change in UPP was significantly smaller in aged rats (60%) and middle‐aged rats (64%) than in young rats. Furthermore, the mean amplitude of high‐frequency oscillations of the EUS was significantly lower in aged (61%) and middle‐aged rats (70%) than in young rats. EUS‐EMG revealed EUS bursting activity during voiding with clear active and silent phases in young rats but unclear active and silent phases in aged rats. Masson's trichrome staining of the urethra showed EUS atrophy in aged rats compared to young and middle‐aged rats. The results indicate that aging induces two urethral dysfunctions in the urethral smooth muscle and EUS, which may lead to dyscoordination between the urinary bladder and urethra.

Health Qigong Mawangdui Guidance can improve pelvic floor muscle function and quality of life in females with stress urinary incontinence: A randomized controlled trial pilot study

“…[27] Also, "tucking in the buttocks" can activate gluteal muscles, pelvic floor muscles, and ligaments. Active contraction training for these muscles can effectively improve the muscle strength and tension of pelvic floor muscles, especially the active contraction of the levator anus, anus, and external urethral sphincter can improve the ability of urine control, [28][29][30][31] which is the key strategy of the treatment of SUI. "Longdeng," the fourth movement of Mawangdui Guidance, is the corresponding Spleen Meridian of Foot-Taiyin.…”

Age is associated with reduced urethral pressure and afferent activity in rat

“…Our results showed that the same flow rates evoked less pressure (correlated with tension) in the urethra in older animals. The increased external urethral sphincter (EUS) connective tissue, reduced number of EUS fibers (Yanai‐Inamura et al, 2019 ) and EUS muscle atrophy (Oshiro et al, 2021 ) with age might explain the reduced pressure generated by urethral infusion in older animals.…”

“…Structural and biochemical changes of nerve fibers and the reduction of regenerative and reinnervating capabilities that come with age impairs the central and peripheral nervous system (Verdú et al, 2000 ), which might affect the LUT reflexes. Oshiro et al ( 2021 ) showed external urethral sphincter atrophy in aged rats, and urethral sphincter muscle fibers appear to be replaced by connective tissue throughout aging (Yanai‐Inamura et al, 2019 ), both of which could lead to a more compliant urethra. Histological studies also showed a decline in number and density of striated urethral sphincter nerve and muscle fibers with age (Perucchini, DeLancey, Ashton‐Miller, Galecki, et al, 2002 ; Perucchini, DeLancey, Ashton‐Miller, Peschers, et al, 2002 ).…”