Best practices for cystometric evaluation of lower urinary tract function in muriform rodents

Bladder responses to thoracolumbar epidural stimulation in female urethane-anesthetized rats with graded contusion spinal cord injuries

Spinal cord epidural stimulation (scES) is a therapeutic option that promotes functional improvements in sensory, motor, and autonomic functions following spinal cord injury (SCI). Previous scES mapping studies targeting the lower urinary tract (LUT) in rats demonstrated functional response variability based upon lumbosacral level, parameters used, extent of injury (spinally intact versus chronic anatomically complete spinal transections), and sex. In the current study, female rats with clinically relevant graded incomplete T9 contusion injuries were mapped with scES at 60 days-post-injury at three spinal levels (T13, L3, L6) with a novel miniature 15-electrode array designed to deliver optimal specificity. The results obtained during bladder fill and void cycles conducted under urethane anesthesia indicate frequency dependent sub-motor threshold effects on LUT function with a single row of electrodes positioned across the full medio-lateral extent of the dorsal cord. The findings of improved storage and emptying, represented by significantly longer inter-contractile intervals with T13 scES and L3 scES and by a significantly increased estimated void efficiency with L6 scES, respectively, is consistent with previous studies using intact and chronic complete transected male and female rats. The data support the efficacy of selective spinal network stimulation to drive functionally relevant networks for storage versus emptying phases of the urinary cycle. The current findings further demonstrate the translational promise of scES for SCI individuals with LUT dysfunctions, regardless of injury severity.

Effect of photobiomodulation on lower urinary tract dysfunction in rat cystitis model

OBJECTIVE

Photobiomodulation selectively controls the activity of the sensory nervous system associated with A-delta and C fibers. Hypersensitivity involving the afferent A-delta and C fibers occurs in cystitis and decreases urinary function. This study aimed to investigate the effect of photobiomodulation on urinary storage dysfunction and voiding functions in cystitis model rats.

METHODS

We prepared the rat cystitis model. Under anesthesia, a cannula was connected to the bladder via a ventral incision. 0.3% acetic acid or saline was injected into the bladder. Continuous cystometry was performed, measuring bladder pressure and voiding urine volume with rats freely mobile. Laser irradiation was applied to the L6 lumbosacral intervertebral foramen using an 830 nm laser. Residual urine was extracted post-cystometry.

RESULTS

In the rat cystitis model groups, there was a significant decrease in the voiding interval and volume compared to the group receiving normal saline infusion. After sham or laser irradiation, only the group with laser irradiation showed a significant increase in voiding interval (217%, p = 0.0002) and voiding volume (192%, p = 0.0012) in the parameters of storage dysfunction. The basal pressure, intravesical pressure, and residual urine volume remained unchanged in all groups before and after irradiation.

CONCLUSIONS

This study indicates that photobiomodulation may improve urine storage dysfunction without exacerbating voiding function in a rat model of cystitis. Thus, photobiomodulation may be a new treatment option for the hypersensitivity and detrusor overactivity caused by cystitis.

Long-term follow-up of TREK-1 KO mice reveals the development of bladder hypertrophy and impaired bladder smooth muscle contractility with age

Stretch-activated two-pore domain K+ (K2P) channels play important roles in many visceral organs, including the urinary bladder. The TWIK-related K+ channel TREK-1 is the predominantly expressed K2P channel in the urinary bladder of humans and rodents. Downregulation of TREK-1 channels was observed in the urinary bladder of patients with detrusor overactivity, suggesting their involvement in the pathogenesis of voiding dysfunction. This study aimed to characterize the long-term effects of TREK-1 on bladder function with global and smooth muscle-specific TREK-1 knockout (KO) mice. Bladder morphology, bladder smooth muscle (BSM) contractility, and voiding patterns were evaluated up to 12 mo of age. Both sexes were included in this study to probe the potential sex differences. Smooth muscle-specific TREK-1 KO mice were used to distinguish the effects of TREK-1 downregulation in BSM from the neural pathways involved in the control of bladder contraction and relaxation. TREK-1 KO mice developed enlarged urinary bladders (by 60.0% for males and by 45.1% for females at 6 mo; P < 0.001 compared with the age-matched control group) and had a significantly increased bladder capacity (by 137.7% at 12 mo; P < 0.0001) and compliance (by 73.4% at 12 mo; P < 0.0001). Bladder strips isolated from TREK-1 KO mice exhibited decreased contractility (peak force after KCl at 6 mo was 1.6 ± 0.7 N/g compared with 3.4 ± 2.0 N/g in the control group; P = 0.0005). The lack of TREK-1 channels exclusively in BSM did not replicate the bladder phenotype observed in TREK-1 KO mice, suggesting a strong neurogenic origin of TREK-1-related bladder dysfunction.NEW & NOTEWORTHY This study compared voiding function and bladder phenotypes in global and smooth muscle-specific TREK-1 KO mice. We found significant age-related changes in bladder contractility, suggesting that the lack of TREK-1 channel activity might contribute to age-related changes in bladder smooth muscle physiology.

Selective recording of physiologically evoked neural activity in a mixed autonomic nerve using a minimally invasive array

Real-time closed-loop control of neuromodulation devices requires long-term monitoring of neural activity in the peripheral nervous system. Although many signal extraction methods exist, few are both clinically viable and designed for extracting small signals from fragile peripheral visceral nerves. Here, we report that our minimally invasive recording and analysis technology extracts low to negative signal to noise ratio (SNR) neural activity from a visceral nerve with a high degree of specificity for fiber type and class. Complex activity was recorded from the rat pelvic nerve that was physiologically evoked during controlled bladder filling and voiding, in an extensively characterized in vivo model that provided an excellent test bed to validate our technology. Urethane-anesthetized male rats (n = 12) were implanted with a four-electrode planar array and the bladder instrumented for continuous-flow cystometry, which measures urodynamic function by recording bladder pressure changes during constant infusion of saline. We demonstrated that differential bipolar recordings and cross-correlation analyses extracts afferent and efferent activity, and discriminated between subpopulations of fibers based on conduction velocity. Integrated Aδ afferent fiber activity correlated with bladder pressure during voiding (r2: 0.66 ± 0.06) and was not affected by activating nociceptive afferents with intravesical capsaicin (r2: 0.59 ± 0.14, P = 0.54, and n = 3). Collectively, these results demonstrate our minimally invasive recording and analysis technology is selective in extracting mixed neural activity with low/negative SNR. Furthermore, integrated afferent activity reliably correlates with bladder pressure and is a promising first step in developing closed-loop technology for bladder control.

Aging and urinary control: Alterations in the brain-bladder axis

Age-associated alterations in bladder control affect millions of older adults, with a heavy burden added to families both economically and in quality of life. Therapeutic options are limited with poor efficacy in older adults, lending to a growing need to address the gaps in our current understanding of urinary tract aging. This review summarizes the current knowledge of age-associated alterations in the structure and function of the brain-bladder axis and identifies important gaps in the field that have yet to be addressed. Urinary aging is associated with decreased tissue responsiveness, decreased control over the voiding reflex, signaling dysfunction along the brain-bladder axis, and structural changes within the bladder wall. Studies are needed to improve our understanding of how age affects the brain-bladder axis and identify genetic targets that correlate with functional outcomes.

Reflex voiding in rat occurs at consistent bladder volume regardless of pressure or infusion rate

AIMS

The central nervous system (CNS) regulates lower urinary tract reflexes using information from sensory afferents; however, the mechanisms of this process are not well known. Pressure and volume were measured at the onset of the guarding and micturition reflexes across a range of infusion rates to provide insight into what the CNS is gauging to activate reflexes.

METHODS

Female Sprague Dawley rats were anesthetized with urethane for open outlet cystometry. A set of 10 infusion rates (ranging 0.92-65.5 mL/h) were pseudo-randomly distributed across 30 single-fill cystometrograms. Bladder pressure and external urethral sphincter electromyography were used for the determination of the onset of the micturition and guarding reflexes, respectively. The bladder volume at the onset of both reflexes was estimated from the total infusion rate during a single fill.

RESULTS

In response to many single-fill cystometrograms, there was an increased volume the bladder could store without a significant increase in pressure. Volume was adjusted for this effect for the analysis of how pressure and volume varied with infusion rate at the onset of the micturition and guarding reflexes. In 25 rats, the micturition reflex was evoked at similar volumes across all infusion rates, whereas the pressure at micturition reflex onset increased with increasing infusion rates. In 11 rats, the guarding reflex was evoked at similar pressures across infusion rates, but the volume decreased with increasing infusion rates.

CONCLUSIONS

These results suggest that the CNS is interpreting volume from the bladder to activate the micturition reflex and pressure from the bladder to activate the guarding reflex.

Mid-lumbar (L3) epidural stimulation effects on bladder and external urethral sphincter in non-injured and chronically transected urethane-anesthetized rats

Recent pre-clinical and clinical spinal cord epidural stimulation (scES) experiments specifically targeting the thoracolumbar and lumbosacral circuitries mediating lower urinary tract (LUT) function have shown improvements in storage, detrusor pressure, and emptying. With the existence of a lumbar spinal coordinating center in rats that is involved with external urethral sphincter (EUS) functionality during micturition, the mid-lumbar spinal cord (specifically L3) was targeted in the current study with scES to determine if the EUS and thus the void pattern could be modulated, using both intact and chronic complete spinal cord injured female rats under urethane anesthesia. L3 scES at select frequencies and intensities of stimulation produced a reduction in void volumes and EUS burst duration in intact rats. After chronic transection, three different subgroups of LUT dysfunction were identified and the response to L3 scES promoted different cystometry outcomes, including changes in EUS bursting. The current findings suggest that scES at the L3 level can generate functional neuromodulation of both the urinary bladder and the EUS in intact and SCI rats to enhance voiding in a variety of clinical scenarios.

Assessing Neurogenic Lower Urinary Tract Dysfunction after Spinal Cord Injury: Animal Models in Preclinical Neuro-Urology Research

Neurogenic bladder dysfunction is a condition that affects both bladder storage and voiding function and remains one of the leading causes of morbidity after spinal cord injury (SCI). The vast majority of individuals with severe SCI develop neurogenic lower urinary tract dysfunction (NLUTD), with symptoms ranging from neurogenic detrusor overactivity, detrusor sphincter dyssynergia, or sphincter underactivity depending on the location and extent of the spinal lesion. Animal models are critical to our fundamental understanding of lower urinary tract function and its dysfunction after SCI, in addition to providing a platform for the assessment of potential therapies. Given the need to develop and evaluate novel assessment tools, as well as therapeutic approaches in animal models of SCI prior to human translation, urodynamics assessment techniques have been implemented to measure NLUTD function in a variety of animals, including rats, mice, cats, dogs and pigs. In this narrative review, we summarize the literature on the use of animal models for cystometry testing in the assessment of SCI-related NLUTD. We also discuss the advantages and disadvantages of various animal models, and opportunities for future research.

Molecular Mechanism Operating in Animal Models of Neurogenic Detrusor Overactivity: A Systematic Review Focusing on Bladder Dysfunction of Neurogenic Origin

Neurogenic detrusor overactivity (NDO) is a severe lower urinary tract disorder, characterized by urinary urgency, retention, and incontinence, as a result of a neurologic lesion that results in damage in neuronal pathways controlling micturition. The purpose of this review is to provide a comprehensive framework of the currently used animal models for the investigation of this disorder, focusing on the molecular mechanisms of NDO. An electronic search was performed with PubMed and Scopus for literature describing animal models of NDO used in the last 10 years. The search retrieved 648 articles, of which reviews and non-original articles were excluded. After careful selection, 51 studies were included for analysis. Spinal cord injury (SCI) was the most frequently used model to study NDO, followed by animal models of neurodegenerative disorders, meningomyelocele, and stroke. Rats were the most commonly used animal, particularly females. Most studies evaluated bladder function through urodynamic methods, with awake cystometry being particularly preferred. Several molecular mechanisms have been identified, including changes in inflammatory processes, regulation of cell survival, and neuronal receptors. In the NDO bladder, inflammatory markers, apoptosis-related factors, and ischemia- and fibrosis-related molecules were found to be upregulated. Purinergic, cholinergic, and adrenergic receptors were downregulated, as most neuronal markers. In neuronal tissue, neurotrophic factors, apoptosis-related factors, and ischemia-associated molecules are increased, as well as markers of microglial and astrocytes at lesion sites. Animal models of NDO have been crucial for understanding the pathophysiology of lower urinary tract (LUT) dysfunction. Despite the heterogeneity of animal models for NDO onset, most studies rely on traumatic SCI models rather than other NDO-driven pathologies, which may result in some issues when translating pre-clinical observations to clinical settings other than SCI.

Initiating daily acute intermittent hypoxia (dAIH) therapy at 1-week after contusion spinal cord injury (SCI) improves lower urinary tract function in rat

Spinal cord injury (SCI) above the level of the lumbosacral spinal cord produces lower urinary tract (LUT) dysfunction, resulting in impairment of urine storage and elimination (voiding). While spontaneous functional recovery occurs due to remodeling of spinal reflex micturition pathways, it is incomplete, indicating that additional strategies to further augment neural plasticity following SCI are essential. To this end, acute intermittent hypoxia (AIH) exposure has been proposed as a therapeutic strategy for improving recovery of respiratory and other somatic motor function following SCI; however, the impact of AIH as a therapeutic intervention to improve LUT dysfunction remains to be determined. Therefore, we examined the effects of daily AIH (dAIH) on both spontaneous micturition patterns and reflex micturition event (rME) behaviors in adult female Sprague-Dawley rats with mid-thoracic moderate contusion SCI. For these experiments, dAIH gas exposures (five alternating 3 min 12% O₂ and 21% O₂ episodes) were delivered for 7 consecutive days beginning at 1-week after SCI, with awake micturition patterns being evaluated weekly for 2-3 sessions before and for 4 weeks after SCI and rME behaviors elicited by continuous infusion of saline into the bladder being evaluated under urethane anesthesia at 4-weeks after SCI; daily normoxia (dNx; 21% O₂ episodes) served as a control. At 1-week post-SCI, both an areflexic phenotype (i.e., no effective voiding events) and a functional voiding phenotype (i.e., infrequent voiding events with large volumes) were observed in spontaneous micturition patterns (as expected), and subsequent dAIH, but not dNx, treatment led to recovery of spontaneous void frequency pattern to pre-SCI levels; both dAIH- and dNx-treated rats exhibited slightly increased void volumes. At 4-weeks post-SCI, rME behaviors showed increased effectiveness in voiding in dAIH-treated (compared to dNx-treated) rats that included an increase in both bladder contraction pressure (delta BP; P = 0.014) and dynamic voiding efficiency (P = 0.018). Based on the voiding and non-voiding bladder contraction behaviors (VC and NVC, respectively) observed in the BP records, bladder dysfunction severity was classified into mild, moderate, and severe phenotypes, and while rats in both treatment groups included each severity phenotype, the primary phenotype observed in dAIH-treated rats was mild and that in dNx-treated rats was moderate (P = 0.044). Taken together, these findings suggest that 7-day dAIH treatment produces beneficial improvements in LUT function that include recovery of micturition pattern, more efficient voiding, and decreased NVCs, and extend support to the use of dAIH therapy to treat SCI-induced LUT dysfunction.

Molecular and Morphological Characteristics of the De-Obstructed Rat Urinary Bladder—An Update

Many patients with outlet obstruction secondary to prostatic enlargement have lower urinary tract symptoms (LUTSs) and an increased frequency of micturition. The standard treatment is transurethral resection of the prostate (TURP), which alleviates obstruction and symptoms. However, after TURP, 20–40 percent of patients continue to experience LUTSs. The aim of the present study in rats was to identify the mechanisms that do not normalize after the removal of the obstruction and that could explain the persisting symptoms. We had microarray data from control, obstructed, and de-obstructed female rat bladders, which made it possible to study 14,553 mRNA expressions. We also had a bank of electron micrographs from similar detrusors. Microarrays: There were significant differences between the control and obstructed bladders for 1111 mRNAs. The obstructed and de-obstructed bladders differed significantly for 1059 mRNAs. The controls and the de-obstructed bladders differed significantly for 798 mRNAs. We observed many mRNAs that were increased in the obstructed bladder and then decreased to control levels after de-obstruction, and many mRNAs that were decreased in the obstructed bladder and then increased following de-obstruction. mRNAs that were significantly higher or lower in the de-obstructed bladder than in the control bladder were also found. Ultrastructure: The detrusor cells in the obstructed bladders had cross-sectional areas that were much larger than those in the controls. The control cells had smooth outlines and similar cross-sectional areas. The de-obstructed detrusor cells had larger cross-sectional areas than the controls, as well as corrugated surfaces. The cell areas varied, suggesting that the shrinkage of the de-obstructed cells was not even. We did not find any points of contact of the gap junction plaque type between the detrusor cells. There were abundant finger-like processes between the detrusor cells in the obstructed and in de-obstructed bladders, which were only occasionally found in the control detrusors. They are the only possible localization for gap junction channels. The de-obstructed rat bladder is not an organ with properties intermediate between those of the control and obstructed bladders. Instead, de-obstructed bladders have gene expressions, morphologies, and functional properties of the individual cells and their organization, which make them distinctly different from both control and obstructed bladders.

Serial transurethral cystometry: A novel method for longitudinal evaluation of reflex lower urinary tract function in adult female rats

AIMS

The aim of the study is to develop a minimally invasive method for longitudinal evaluation of lower urinary tract function that allows for simultaneous measurements of bladder pressure and external urethral sphincter (EUS) electromyographic (EMG) activity.

METHODS

To evaluate the reliability of serial transurethral cystometry (STUC), rats (n = 12) underwent three sessions of STUC, one session a week for 3 weeks. During each session, rats were anesthetized with ketamine-xylazine (90 mg/kg and 10 mg/kg), and micturition reflex data were acquired using transurethral cystometry and percutaneous recording of EUS (EMG) activity during continuous infusion of saline into the bladder. The reliability and consistency of the STUC method were assessed using intra-class correlation (ICC) analysis and repeated measures ANOVA.

RESULTS

ICC values calculated from five successive events during the first micturition session indicate good to excellent reliability for measurements of peak bladder pressure, threshold bladder pressure, minimum bladder pressure, volume threshold, duration of EUS bursting, and number of EUS burst events. Across the three recording sessions no significant difference was observed in peak bladder pressure, threshold bladder pressure, minimum bladder pressure, volume threshold, number of EUS burst events, and duration of EUS bursting using repeated measures ANOVA.

CONCLUSION

Serial transurethral cystometry under ketamine-xylazine anesthesia with simultaneous percutaneous EUS EMG recording is a novel, reliable, accurate, and minimally invasive method for quantitative assessment of lower urinary tract (LUT) function in adult female rats over extended periods of time.

The Aged Lower Urinary Tract: Deficits in Neural Control Mechanisms

Bothersome urinary symptoms plague many older adults and disproportionally affect women. Underreporting of symptoms and general stigma/embarrassment associated with incontinence has negatively impacted the availability of treatments, as research cannot be championed if the severity of the problem is not apparent. Available therapeutics have limited efficacy and are often not recommended in aged patients. Lower urinary tract function has a long and rich history in animal studies; while much of the underlying anatomy has been described, including neural control mechanisms, the impact of aging has only just begun to be addressed. Recent work has provided strong evidence that neural control over micturition is significantly impacted by aging processes. This mini review discusses recent findings regarding how aging impacts the neural control mechanisms of micturition.

Metformin abrogates the voiding dysfunction induced by prolonged methylglyoxal intake

Methylglyoxal (MGO) is a reactive carbonyl species found at high levels in blood of diabetic patients. The anti-hyperglycemic drug metformin can scavenger MGO and reduce the formation of advanced glycation end products (AGEs). Here, we aimed to investigate if MGO-induced bladder dysfunction can be reversed by metformin. Male C57/BL6 mice received 0.5% MGO in drinking water for 12 weeks, and metformin (300 mg/kg, daily gavage) was given in the last two weeks. The bladder functions were evaluated by performing voiding behavior assays, cystometry and in vitro bladder contractions. MGO intake markedly elevated the levels of MGO and fluorescent AGEs in serum and reduced the mRNA expression and activity of glyoxalase (Glo1) in bladder tissues. Glucose levels were unaffected among groups. MGO intake also increased the urothelium thickness and collagen content of the bladder. Void spot assays in conscious mice revealed an increased void volume in MGO group. The cystometric assays in anesthetized mice revealed increases of basal pressure, non-voiding contractions frequency, bladder capacity, inter-micturition pressure and residual volume, which were accompanied by reduced voiding efficiency in MGO group. In vitro bladder contractions to carbachol, α,β-methylene ATP and electrical-field stimulation were significantly greater in MGO group. Metformin normalized the changes of MGO and AGEs levels, Glo1 expression and activity, urothelium thickness and collagen content. The MGO-induced voiding dysfunction were all restored by metformin treatment. Our findings strongly suggest that the amelioration of MGO-induced voiding dysfunction by metformin relies on its ability to scavenger MGO, preventing its accumulation in blood.

Transurethral versus suprapubic catheterization to test urethral function in rats

Transurethral and suprapubic catheterization have both been used to test urethral function in rats; however, it is unknown whether these methods affect urethral function or if the order of catheterization affects the results. The aim of this cross-over designed experiment was to compare the effects of catheterization methods and order on leak point pressure (LPP) testing. LPP and simultaneous external urethral sphincter electromyography (EUS EMG) were recorded in anesthetized female virgin Sprague-Dawley rats in a cross-over design to test the effects of transurethral and suprapubic catheterization. There was no significant difference in peak bladder pressure during LPP testing whether measured with a transurethral or suprapubic catheter. There was no significant difference in peak bladder pressure between the first and second catheter insertions. However, peak EMG firing rate, as well as peak EMG amplitude and EMG amplitude difference between peak and baseline were significantly higher after the first catheter insertion compared to the second insertion, regardless of the catheter method. Our results suggest that route of catheterization does not alter urethral function, e.g. create a functional partial outlet obstruction. Either catheterization method could be used for LPP and/or EUS EMG testing in rats.

X-ray videocystometry for high-speed monitoring of urinary tract function in mice

Lower urinary tract dysfunction (LUTd) represents a major health care problem with a high, unmet medical need. Design of additional therapies for LUTd requires precise tools to study bladder storage and voiding (dys)function in animal models. We developed videocystometry in mice, combining intravesical pressure measurements with high-speed fluoroscopy of the urinary tract. Videocystometry substantially outperforms current state-of-the-art methods to monitor the urine storage and voiding process, by enabling quantitative analysis of voiding efficiency, urethral flow, vesicoureteral reflux, and the relation between intravesical pressure and flow, in both anesthetized and awake, nonrestrained mice. Using videocystometry, we identified localized bladder wall micromotions correlated with different states of the filling/voiding cycle, revealed an acute effect of TRPV1 channel activation on voiding efficiency, and pinpointed the effects of urethane anesthesia on urine storage and urethral flow. Videocystometry has broad applications, ranging from the elucidation of molecular mechanisms of bladder control to drug development for LUTd.

Genetic background but not prostatic epithelial beta-catenin influences susceptibility of male mice to testosterone and estradiol-induced urinary dysfunction

Urinary voiding dysfunction in aging men can cause bothersome symptoms and irreparable tissue damage. Underlying mechanisms are not fully known. We previously demonstrated that subcutaneous, slow-release testosterone and estradiol implants (T+E2) drive a pattern of urinary voiding dysfunction in male mice that resembles that of aging men. The initial goal of this study was to test the hypothesis that prostatic epithelial beta-catenin (Ctnnb1) is required for T+E2-mediated voiding dysfunction. Targeted Ctnnb1 deletion did not significantly change voiding function in control or T+E2 treated mice but led to the surprising discovery that the C57BL/6J × FVB/NJ × 129S1 mixed genetic background onto which Ctnnb1 loss of function alleles were maintained is profoundly susceptible to voiding dysfunction. The mixed background mice develop a more rapid T+E2-mediated increase in spontaneous urine spotting, are more impaired in ability to initiate bladder contraction, and develop larger and heavier bladders than T+E2 treated C57BL/6J pure bred mice. To better understand mechanisms, we separately evaluated contributions of T and E2 and found that E2 mediates voiding dysfunction. Our findings that genetic factors serve as modifiers of responsiveness to T and E2 demonstrate the need to control for genetic background in studies of male voiding dysfunction. We also show that genetic factors could control severity of voiding dysfunction. We demonstrate the importance of E2 as a key mediator of voiding impairment, and show that the concentration of E2 in subcutaneous implants determines the severity of voiding dysfunction in mice, demonstrating that the mouse model is tunable, a factor which is important for future pharmacological intervention studies.

Bladder and bowel responses to lumbosacral epidural stimulation in uninjured and transected anesthetized rats

Spinal cord epidural stimulation (scES) mapping at L5-S1 was performed to identify parameters for bladder and bowel inhibition and/or contraction. Using spinally intact and chronic transected rats of both sexes in acute urethane-anesthetized terminal preparations, scES was systematically applied using a modified Specify 5-6-5 (Medtronic) electrode during bladder filling/emptying cycles while recording bladder and colorectal pressures and external urethral and anal sphincter electromyography activity. The results indicate frequency-dependent effects on void volume, micturition, bowel peristalsis, and sphincter activity just above visualized movement threshold intensities that differed depending upon neurological intactness, with some sex-dependent differences. Thereafter, a custom-designed miniature 15-electrode array designed for greater selectivity was tested and exhibited the same frequency-dependent urinary effects over a much smaller surface area without any concurrent movements. Thus, select activation of autonomic nervous system circuitries with scES is a promising neuromodulation approach for expedient translation to individuals with SCI and potentially other neurologic disorders.

Choice of cystometric technique impacts detrusor contractile dynamics in wistar rats

The objective of the current animal study was to investigate factors contributing to the different phases of the cystometrogram (CMG) in order to address disparities in research data reported in the current literature. Three experiments in 20 female Wistar rats were designed to investigate (1) the effects of anesthesia on the contractile pattern of the bladder during micturition; (2) the impact of the physical characteristics of the CMG technique upon the accuracy of intra-vesical pressure recordings; and (3) identification of physiological and methodological factors associated with the emptying and rebound phases during CMG. Variables tested included awake versus urethane-anesthetized conditions, use of a single catheter for both filling and intra-vesical pressure (Pves) recording versus a separate two catheter approach, and comparisons between ureter, bladder dome, and urethral catheter placements. Both awake and anesthetized conditions contributed to variations in the shape and magnitude of the CMG pressure curves. In addition, catheter size, acute incision of the bladder dome for catheter placement, use of the same catheter for filling and Pves recordings, as well as the placement and positioning of the tubing, all contributed to alterations of the physiological properties and characteristic of the various CMG phases, including the frequent occurrence of an artificial rebound during the third phase of micturition. The present results demonstrate how different experimental conditions lead not only to variability in Pves curves, but consistency of the measurements as well, which needs to be accounted for when interpreting CMG outcome data.

A uropathogenic E. coli UTI89 model of prostatic inflammation and collagen accumulation for use in studying aberrant collagen production in the prostate

Bacterial infection is one known etiology of prostatic inflammation. Prostatic inflammation is associated with prostatic collagen accumulation and both are linked to progressive lower urinary tract symptoms in men. We characterized a model of prostatic inflammation using transurethral instillations of Escherichia coli UTI89 in C57BL/6J male mice with the goal of determining the optimal instillation conditions, understanding the impact of instillation conditions on urinary physiology, and identifying ideal prostatic lobes and collagen 1a1 prostatic cell types for further analysis. The smallest instillation volume tested (50 µL) distributed exclusively to the bladder, 100- and 200-µL volumes distributed to the bladder and prostate, and a 500-µL volume distributed to the bladder, prostate, and ureter. A threshold optical density of 0.4 E. coli UTI89 in the instillation fluid was necessary for significant (P < 0.05) prostate colonization. E. coli UTI89 infection resulted in a low frequency, high volume spontaneous voiding pattern. This phenotype was due to exposure to E. coli UTI89, not catheterization alone, and was minimally altered by a 50-µL increase in instillation volume and doubling of E. coli concentration. Prostate inflammation was isolated to the dorsal prostate and was accompanied by increased collagen density. This was partnered with increased density of protein tyrosine phosphatase receptor type C+, procollagen type I-α1+ copositive cells and decreased density of α2-smooth muscle actin+, procollagen type I-α1+ copositive cells. Overall, we determined that this model is effective in altering urinary phenotype and producing prostatic inflammation and collagen accumulation in mice.

Recording of Electrically Evoked Neural Activity and Bladder Pressure Responses in Awake Rats Chronically Implanted With a Pelvic Nerve Array

Bioelectronic medical devices are well established and widely used in the treatment of urological dysfunction. Approved targets include the sacral S3 spinal root and posterior tibial nerve, but an alternate target is the group of pelvic splanchnic nerves, as these contain sacral visceral sensory and autonomic motor pathways that coordinate storage and voiding functions of the bladder. Here, we developed a device suitable for long-term use in an awake rat model to study electrical neuromodulation of the pelvic nerve (homolog of the human pelvic splanchnic nerves). In male Sprague-Dawley rats, custom planar four-electrode arrays were implanted over the distal end of the pelvic nerve, close to the major pelvic ganglion. Electrically evoked compound action potentials (ECAPs) were reliably detected under anesthesia and in chronically implanted, awake rats up to 8 weeks post-surgery. ECAP waveforms showed three peaks, with latencies that suggested electrical stimulation activated several subpopulations of myelinated A-fiber and unmyelinated C-fiber axons. Chronic implantation of the array did not impact on voiding evoked in awake rats by continuous cystometry, where void parameters were comparable to those published in naïve rats. Electrical stimulation with chronically implanted arrays also induced two classes of bladder pressure responses detected by continuous flow cystometry in awake rats: voiding contractions and non-voiding contractions. No evidence of tissue pathology produced by chronically implanted arrays was detected by immunohistochemical visualization of markers for neuronal injury or noxious spinal cord activation. These results demonstrate a rat pelvic nerve electrode array that can be used for preclinical development of closed loop neuromodulation devices targeting the pelvic nerve as a therapy for neuro-urological dysfunction.

Blockade of Acid-Sensing Ion Channels Increases Urinary Bladder Capacity With or Without Intravesical Irritation in Mice

We conducted this study to examine whether acid-sensing ion channels (ASICs) are involved in the modulation of urinary bladder activity with or without intravesical irritation induced by acetic acid. All in vivo evaluations were conducted during continuous infusion cystometry in decerebrated unanesthetized female mice. During cystometry with a pH 6.3 saline infusion, an i.p. injection of 30 μmol/kg A-317567 (a potent, non-amiloride ASIC blocker) increased the intercontraction interval (ICI) by 30% (P < 0.001), whereas vehicle injection had no effect. An intravesical acetic acid (pH 3.0) infusion induced bladder hyperactivity, with reductions in ICI and maximal voiding pressure (MVP) by 79% (P < 0.0001) and 29% (P < 0.001), respectively. A-317567 (30 μmol/kg i.p.) alleviated hyperreflexia by increasing the acid-shortened ICI by 76% (P < 0.001). This dose produced no effect on MVP under either intravesical pH condition. Further analysis in comparison with vehicle showed that the increase in ICI (or bladder capacity) by the drug was not dependent on bladder compliance. Meanwhile, intravesical perfusion of A-317567 (100 μM) had no effect on bladder activity during pH 6.0 saline infusion cystometry, and drug perfusion at neither 100 μM nor 1 mM produced any effects on bladder hyperreflexia during pH 3.0 acetic acid infusion cystometry. A-317567 has been suggested to display extremely poor penetrability into the central nervous system and thus to be a peripherally active blocker. Taken together, our results suggest that blockade of ASIC signal transduction increases bladder capacity under normal intravesical pH conditions and alleviates bladder hyperreflexia induced by intravesical acidification and that the site responsible for this action is likely to be the dorsal root ganglia.