External Urethral Sphincter Electromyography Activity Research Articles

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

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.

Investigations of urethral sphincter activity in mice with bladder hyperalgesia before and after drug administration of gabapentin.

This study investigated the effect of gabapentin on lower urinary tract dysfunction focusing on urethral activities and cystitis-induced hyperalgesia in a mouse model of painful bladder syndrome/interstitial cystitis (PBS/IC). The electromyography(EMG) of external urethral sphincter(EUS) was difficult to obtain, but contained useful information to examine the drug effect in mice. Female C57BL/6J mice were intraperitoneally (ip) administration with either saline or 200mg/kg of cyclophosphamide (CYP) 48h before experimental evaluation. Cystitis mice were treated with administration of gabapentin (25 or 50mg/kg, ip). Cystometry and EUS EMG were obtained and analyzed during continuous bladder infusion. The visceral pain-related visceromotor reflex (VMR) was recorded in response to isotonic bladder distension. Cystitis mice showed shorter inter-contraction intervals and increased occurrence of non-voiding contractions during bladder infusion, with increased VMR during isotonic bladder distension, indicating cystitis-induced bladder hyperalgesia. Gabapentin (50mg/kg) suppressed effects of CYP on cystometry, but not on EUS EMG activity, during bladder infusion. The effect on urodynamic recordings lasted 4h. VMR was significantly reduced by gabapentin. The present study showed that CYP-induced cystitis in mice is a model of visceral hyperalgesia affecting detrusor contractions, not urethral activations. The technique of using EUSEMG to evaluate the drug effects on urethral activities is novel and useful for future investigations. Gabapentin can be as a potential treatment for detrusor overactivity and PBS/IC.

Combined Cystometrography and Electromyography of the External Urethral Sphincter Following Complete Primary Repair of Bladder Exstrophy

Concern in patients with bladder exstrophy after reconstruction regarding potential injury to pelvic neurourological anatomy and a resultant functional deficit prompted combined (simultaneous) cystometrography and electromyography after complete primary repair of bladder exstrophy. We determined whether complete primary repair of bladder exstrophy would adversely affect the innervation controlling bladder and external urethral sphincter function. Complete primary repair of bladder exstrophy was performed via a modified Mitchell technique in newborns without osteotomy. Postoperative evaluation included combined cystometrography and needle electrode electromyography via the perineum, approximating the external urethral sphincter muscle complex. Electromyography was done to evaluate the external urethral sphincter response to sacral reflex stimulation and during voiding. Nine boys and 4 girls underwent combined cystometrography/electromyography after complete primary repair of bladder exstrophy. Age at study and time after complete primary repair of bladder exstrophy was 3 months to 10 years (median 11.5 months). Cystometrography revealed absent detrusor overactivity and the presence of a sustained detrusor voiding contraction in all cases. Electromyography showed universally normal individual motor unit action potentials of biphasic pattern, amplitude and duration. The external urethral sphincter sacral reflex response was intact with a normal caliber with respect to Valsalva, Credé, bulbocavernosus and anocutaneous (bilateral) stimulation. Synergy was documented by abrupt silencing of external urethral sphincter electromyography activity during voiding. After complete primary repair of bladder exstrophy combined cystometrography/electromyography in patients with bladder exstrophy showed normal neurourological findings, including sacral reflex responses, sustained detrusor voiding contraction and synergic voiding, in all patients postoperatively. These findings confirm the safety of complete primary repair of bladder exstrophy. Based on our results we have discontinued routine electromyography in these patients.

Quantitative evaluation of electrodes for external urethral sphincter electromyography during bladder-to-urethral guarding reflex

Accuracy in the recording of external urethral sphincter (EUS) electromyography (EMG) is an important goal in the quantitative evaluation of urethral function. The aim of this study was to quantitatively compare electrode recordings taken during tonic activity and leak point pressure (LPP) testing. Several electrodes, including the surface electrode (SE), concentric electrode (CE), and wire electrode (WE), were placed on the EUS singly and simultaneously in six female Sprague-Dawley rats under urethane anesthesia. The bladder was filled via a retropubic catheter while LPP testing and EUS EMG recording were done. Quantitative baseline correction of the EUS EMG signal was performed to reduce baseline variation. Amplitude and frequency of 1-s samples of the EUS EMG signal were measured before LPP (tonic activity) and during peak LPP activity. The SE, CE, and WE signals demonstrated tonic activity before LPP and an increase in activity during LPP, suggesting that the electrodes accurately recorded EUS activity during tonic activity and during the bladder-to-EUS guarding reflex, regardless of the size or location of detection areas. SE recordings required significantly less baseline correction than both CE and WE recordings. The activity in CE-recorded EMG was significantly higher than that of the SE and WE both in single and simultaneous recordings. These electrodes may be suitable for testing EUS EMG activity. The SE signal had significantly less baseline variation and the CE detected local activity more sensitively than the other electrodes, which may provide insight into choosing an appropriate electrode for EUS EMG recording.

Differential effects of urethane and isoflurane on external urethral sphincter electromyography and cystometry in rats

Urethane is a common and often preferred anesthetic agent for urodynamic recordings in rats, but its use is often restricted to terminal procedures because of a prolonged duration of action and potentially toxic effects. When urodynamic recordings are part of survival procedures in rodent experimental models, inhalation anesthetics, such as isoflurane, are frequently used and generally well tolerated. In this study, we compared the effects of urethane and isoflurane on lower urinary tract function. For this purpose, adult female rats were anesthetized by subcutaneous administration of urethane (n=6) or by inhalation of isoflurane (n=5). Micturition reflexes were assessed by concurrent cystometrogram and external urethral sphincter (EUS) electromyography (EMG) recordings to determine bladder contractile properties, EUS activation patterns, and the coordination between bladder contractions and EUS activation. Compared with urethane, isoflurane reduced frequency of bursts, firing frequency, and amplitude of EUS EMG activity during voiding as well as the EUS EMG amplitude during the bladder filling phase. Isoflurane also prolonged the bladder intercontractile intervals. Other several key functional aspects of the bladder contractile properties as well as the coordination between bladder contractions were not different between the two experimental groups. We conclude that micturition reflexes were differentially affected by isoflurane and urethane. Specifically, isoflurane exhibited a significant suppression of the EUS EMG activity and prolonged the bladder intercontractile intervals compared with urethane. We suggest that these anesthetic properties be taken into consideration during the experimental design and interpretation of urodynamic recordings in rodent models.

Re-established micturition reflexes show differential activation patterns after lumbosacral ventral root avulsion injury and repair in rats

Previous studies have demonstrated that an acute implantation of lesioned lumbosacral ventral roots into the rat conus medullaris (CM) results in functional reinnervation of the lower urinary tract (LUT). Although the root implantation procedure results in a return of reflexive micturition, voiding efficiency (VE) remains incompletely recovered. Here, we performed a detailed urodynamic analysis of cystometry and external urethral sphincter (EUS) electromyography (EMG) recordings to determine underlying mechanisms for the incompletely recovered VE. For this purpose, adult female rats were studied at 12 weeks after a bilateral L5–S2 ventral root avulsion injury followed by an acute surgical implantation of the avulsed L6 and S1 ventral roots into the CM ( n = 6). Age-matched sham-operated rats ( n = 6) were included for control purposes. Compared to sham-operated controls, rats of the implanted series showed 1) reflex bladder contractions with a significantly shortened urine expulsion phase, 2) markedly decreased phasic EUS EMG activity during micturition, and 3) a pronounced bladder–sphincter dys-coordination, as demonstrated by a significantly delayed onset of the switch from low-amplitude tonic EUS EMG activity to either phasic EUS EMG activity or a large-amplitude tonic EUS EMG activity during the urine expulsion phase. Our findings provide a mechanistic explanation for the incomplete recovery of the VE following implantation of avulsed ventral roots into the spinal cord. Our future studies will aim to increase successful axonal regeneration in attempts to augment the recovery of the LUT after cauda equina injury and repair.

A Model of Neural Cross-Talk and Irritation in the Pelvis: Implications for the Overlap of Chronic Pelvic Pain Disorders

Irritable bowel syndrome, interstitial cystitis, and other chronic pelvic pain (CPP) disorders often occur concomitantly. Neural cross-talk may play a role in the overlap of CPP disorders via the convergence of pelvic afferents. We investigated the hypothesis that afferent irritation of one pelvic organ may adversely influence and sensitize another via neural interactions. We measured pelvic organ smooth muscle and striated muscle reflexes during micturition and colorectal distention (CRD) in urethane-anesthetized rats. The effects of acute cystitis on distal colonic sensory thresholds to CRD and the effects of acute colonic irritation on micturition parameters were assessed. External urethral sphincter (EUS) electromyography (EMG) was typical for the rat, with phasic firing during micturition. External anal sphincter EMG also showed phasic firing during micturition in synchrony with EUS activity but, in addition, showed both tonic bursts and phasic firing independent of EUS activity. Before bladder irritation, graded CRDs to 40 cm H2O produced no notable changes in abdominal wall EMG activity. Following acute bladder irritation, dramatic increases in abdominal wall EMG activity in response to CRD were observed at much lower distention pressures, indicating colonic afferent sensitization. Analogously, following acute colonic irritation, bladder contraction frequency increased 66%, suggesting sensitization of lower urinary tract afferents. We report compelling evidence of bidirectional cross-sensitization of the colon and lower urinary tract in a novel experimental model. This cross-sensitization may account for the substantial overlap of CPP disorders; however, further studies are needed to fully characterize these pathways.

BIPHASIC URETHRAL SPHINCTER RESPONSES TO ACETIC ACID INFUSION INTO THE LOWER URINARY TRACT IN ANESTHETIZED CATS

Varying the concentration of infused acetic acid produced bladder irritation and dose dependent increases in external urethral sphincter electromyography activity in cats. We further characterized acetic acid induced external urethral sphincter electromyography activity in intact and acute spinal cord injured animals. Bladder cystometrography and external urethral sphincter electromyography were continuously recorded in chloralose anesthetized cats. Dilute 0.05% to 0.8% acetic acid was infused into the lower urinary tract through the bladder dome. Intravesical or intraurethral infusion was performed separately in bladder neck ligated preparations. In some animals the spinal cord was transected at L1 to L2 2 to 8 hours before the study. Acetic acid infusion into the lower urinary tract elicited dose dependent increases in tonic external urethral sphincter activity. However, a prolonged infusion of 0.7% to 0.8% acetic acid usually inhibited external urethral sphincter activity. The excitatory external urethral sphincter response was elicited by intraurethral but not by intravesical infusion. This response remained in acute spinal cord injured animals. The inhibition of tonic external urethral sphincter activity during 0.7% to 0.8% acetic acid infusion was observed when there was extreme bladder irritation characterized by continual contractions. Induced tonic external urethral sphincter activity was attenuated by intrathecal administration of prazosin or scopolamine and abolished by hexamethonium. Acetic acid infusion into the lower urinary tract elicits biphasic external urethral sphincter responses. The early excitatory response is a spinal urethrourethral reflex and the late inhibitory phase results from negative vesicourethral feedback control. Spinal muscarinic cholinergic and alpha-adrenergic receptors are involved in acetic acid induced excitatory external urethral sphincter responses.