Contribution of the external urethral sphincter to urinary void size in unanesthetized unrestrained rats

Abstract

Aims In anesthetized rats, voiding is typically associated with phasic activation (bursting) of the external urethral sphincter (EUS). During spontaneous voiding in unanesthetized, unrestrained rats, EUS bursting is the most common form of EUS activity exhibited, but it is not necessary for productive voiding to occur. The aim of the present study was to determine which aspects of EUS activity contributed to void size during bursting and non-bursting voiding in conscious, freely moving rats. Methods Female rats were implanted with electrodes adjacent to the EUS for recording electromyographic activity (EMG). EUS EMG recordings were performed during 24-hr sessions in a metabolic cage while voided urine was continuously collected and weighed. Results Void size was positively correlated with the duration of the intra-burst silent and active periods and variables reflecting the overall intensity and duration of bursting, particularly at lower frequencies within the 3–10 Hz range of EUS bursting. In addition, void size was inversely related to the frequency of bursting and to the average EMG amplitude during voiding, both in voids with and without bursting. Conclusions EUS bursting contributes to productive voiding when bursting is present. Lower bursting frequencies elicit more productive voiding than do higher frequencies. In the absence of bursting, the association of increased void size with smaller average EUS EMG amplitude suggests that conscious rats can perform synergic voiding (i.e., bladder contraction with EUS relaxation) that is comparable to that seen in humans and other typically non-bursting species.

Electrical Activity of the Bladder Is Attenuated by Intravesical Inhibition of P2X2/3 Receptors During Micturition in Female Rats

“…Due to the geometry and flexibility of the electrodes, no perforations of the bladder occurred during cystometric filling, providing a greater contact area for signal acquisition than can be accomplished using standard electrodes. As has been observed during electromyographic recordings from the EUS made using needle electrodes [ 16 , 23 ], we noted that electrical activity started before voiding. Interestingly, when bladder pressure and electrical waveforms were superimposed, a consistent trend was observed in which the dome of the bladder was consistently 180° out of phase with the EUS ( Fig.…”

“…Interestingly, a urodynamic model incorporating electromyography of the EUS with bladder pressure monitoring has been developed for LUT evaluation using fully awake rats [ 14 ]. Similarly, a recent study compared the electromyographic characteristics of the EUS with changes in bladder pressure of mice and rats with and without spinal cord injury leading to LUT dysfunction [ 15 , 16 ]. Nevertheless, to the best of our knowledge, no previous study has presented simultaneous recordings of electrical signals in the detrusor and analyzed their associations with changes in bladder pressure and electromyography of the EUS.…”

Smooth Muscle Precursor Cells Derived from Human Pluripotent Stem Cells for Treatment of Stress Urinary Incontinence

“…1). Thus, inadequate EMG activity or excessive crosstalk from other muscles can cause high variability [46]. We did not use the EMG activity at leak point because that measurement is subject to even more uncertainty (Fig.…”

A Method for Recording Urethral Pressure Profiles in Female Rats

“…Most of these methods, with the exception of UPP measurement, have been widely used on small-sized animals, such as rats. LPP measurements and EMG have been successfully performed in anesthetized and fully awake rats [ 1 , 10 , 11 ]. Our methodology provides a simple technique for performing UPP recordings in anesthetized rats.…”

“…Urethral pressure profile (UPP) and leak-point pressure (LPP) assessments as well as external urethral sphincter (EUS) electromyography (EMG), and videourodynamic analyses are the primary methods for evaluating urethral function in humans [ 7 – 12 ]. However, while LPP measurement via suprapubic catheterization and EUS-EMG with surgically implanted electrodes are well-established and generally accepted methods for use in rats, recording UPP in this animal is challenging due to its small body size [ 1 – 6 , 10 – 11 ]. To the best of our knowledge, only one previous study has record UPP curves in female rats, and it was conducted with a 1.4 Fr.…”