Control of urinary drainage and voiding

Research and progress on the mechanism of lower urinary tract neuromodulation: a literature review

The storage and periodic voiding of urine in the lower urinary tract are regulated by a complex neural control system that includes the brain, spinal cord, and peripheral autonomic ganglia. Investigating the neuromodulation mechanisms of the lower urinary tract helps to deepen our understanding of urine storage and voiding processes, reveal the mechanisms underlying lower urinary tract dysfunction, and provide new strategies and insights for the treatment and management of related diseases. However, the current understanding of the neuromodulation mechanisms of the lower urinary tract is still limited, and further research methods are needed to elucidate its mechanisms and potential pathological mechanisms. This article provides an overview of the research progress in the functional study of the lower urinary tract system, as well as the key neural regulatory mechanisms during the micturition process. In addition, the commonly used research methods for studying the regulatory mechanisms of the lower urinary tract and the methods for evaluating lower urinary tract function in rodents are discussed. Finally, the latest advances and prospects of artificial intelligence in the research of neuromodulation mechanisms of the lower urinary tract are discussed. This includes the potential roles of machine learning in the diagnosis of lower urinary tract diseases and intelligent-assisted surgical systems, as well as the application of data mining and pattern recognition techniques in advancing lower urinary tract research. Our aim is to provide researchers with novel strategies and insights for the treatment and management of lower urinary tract dysfunction by conducting in-depth research and gaining a comprehensive understanding of the latest advancements in the neural regulation mechanisms of the lower urinary tract.

Model-based analysis of the acute effects of transcutaneous magnetic spinal cord stimulation on micturition after spinal cord injury in humans

AIM

After spinal cord injuries (SCIs), patients may develop either detrusor-sphincter dyssynergia (DSD) or urinary incontinence, depending on the level of the spinal injury. DSD and incontinence reflect the loss of coordinated neural control among the detrusor muscle, which increases bladder pressure to facilitate urination, and urethral sphincters and pelvic floor muscles, which control the bladder outlet to restrict or permit bladder emptying. Transcutaneous magnetic stimulation (TMS) applied to the spinal cord after SCI reduced DSD and incontinence. We defined, within a mathematical model, the minimum neuronal elements necessary to replicate neurogenic dysfunction of the bladder after a SCI and incorporated into this model the minimum additional neurophysiological features sufficient to replicate the improvements in bladder function associated with lumbar TMS of the spine in patients with SCI.

METHODS

We created a computational model of the neural circuit of micturition based on Hodgkin-Huxley equations that replicated normal bladder function. We added interneurons and increased network complexity to reproduce dysfunctional micturition after SCI, and we increased the density and complexity of interactions of both inhibitory and excitatory lumbar spinal interneurons responsive to TMS to provide a more diverse set of spinal responses to intrinsic and extrinsic activation of spinal interneurons that remains after SCI.

RESULTS

The model reproduced the re-emergence of a spinal voiding reflex after SCI. When we investigated the effect of monophasic and biphasic TMS at two frequencies applied at or below T10, the model replicated the improved coordination between detrusor and external urethral sphincter activity that has been observed clinically: low-frequency TMS (1 Hz) within the model normalized control of voiding after SCI, whereas high-frequency TMS (30 Hz) enhanced urine storage.

CONCLUSION

Neuroplasticity and increased complexity of interactions among lumbar interneurons, beyond what is necessary to simulate normal bladder function, must be present in order to replicate the effects of SCI on control of micturition, and both neuronal and network modifications of lumbar interneurons are essential to understand the mechanisms whereby TMS reduced bladder dysfunction after SCI.

Bladder-draining lymph nodes support germinal center B cell responses during urinary tract infection in mice

Bacterial urinary tract infections (UTIs) are both common and exhibit high recurrence rates in women. UTI healthcare costs are increasing due to the rise of multidrug-resistant (MDR) bacteria, necessitating alternative approaches for infection control. Here, we directly observed host adaptive immune responses in acute UTI. We employed a mouse model in which wild-type C57BL/6J mice were transurethrally inoculated with a clinically relevant MDR UTI strain of uropathogenic Escherichia coli (UPEC). Firstly, we noted that rag1-/- C57BL/6J mice harbored larger bacterial burdens than wild-type counterparts, consistent with a role for adaptive immunity in UTI control. Consistent with this, UTI triggered in the bladders of wild-type mice early increases of myeloid cells, including CD11chi conventional dendritic cells, suggesting possible involvement of these professional antigen-presenting cells. Importantly, germinal center B cell responses developed by 4 weeks post-infection in bladder-draining lymph nodes of wild-type mice and, although modest in magnitude and transient in nature, could not be boosted with a second UTI. Thus, our data reveal for the first time in a mouse model that UPEC UTI induces local B cell immune responses in bladder-draining lymph nodes, which could potentially serve to control infection.

Intracellular signaling pathways of muscarinic acetylcholine receptor-mediated detrusor muscle contractions

Acetylcholine plays an essential role in the regulation of detrusor muscle contractions, and antimuscarinics are widely used in the management of overactive bladder syndrome. However, several adverse effects limit their application and patients' compliance. Thus, this study aimed to further analyze the signal transduction of M2 and M3 receptors in the murine urinary bladder to eventually find more specific therapeutic targets. Experiments were performed on adult male wild-type, M2, M3, M2/M3, or Gαq/11 knockout (KO), and pertussis toxin (PTX)-treated mice. Contraction force and RhoA activity were measured in the urinary bladder smooth muscle (UBSM). Our results indicate that carbamoylcholine (CCh)-induced contractions were associated with increased activity of RhoA and were reduced in the presence of the Rho-associated kinase (ROCK) inhibitor Y-27632 in UBSM. CCh-evoked contractile responses and RhoA activation were markedly reduced in detrusor strips lacking either M2 or M3 receptors and abolished in M2/M3 KO mice. Inhibition of Gαi-coupled signaling by PTX treatment shifted the concentration-response curve of CCh to the right and diminished RhoA activation. CCh-induced contractile responses were markedly decreased in Gαq/11 KO mice; however, RhoA activation was unaffected. In conclusion, cholinergic detrusor contraction and RhoA activation are mediated by both M2 and M3 receptors. Furthermore, whereas both Gαi and Gαq/11 proteins mediate UBSM contraction, the activation at the RhoA-ROCK pathway appears to be linked specifically to Gαi. These findings may aid the identification of more specific therapeutic targets for bladder dysfunctions.NEW & NOTEWORTHY Muscarinic acetylcholine receptors are of utmost importance in physiological regulation of micturition and also in the development of voiding disorders. We demonstrate that the RhoA-Rho-associated kinase (ROCK) pathway plays a crucial role in contractions induced by cholinergic stimulation in detrusor muscle. Activation of RhoA is mediated by both M2 and M3 receptors as well as by Gi but not Gq/11 proteins. The Gi-RhoA-ROCK pathway may provide a novel therapeutic target for overactive voiding disorders.

Association between osteoarthritis and urinary tract infection in older adults: A nationwide population-based cohort study

Osteoarthritis (OA) may increase urinary tract infection (UTI) in older adults. However, this issue remains unclear. We identified 8599 older patients (≥65 years) with OA, and an equal number of older patients without OA, matched by age, sex, and index date from the Taiwan National Health Insurance Research Database between 2001 and 2005. Past histories, including UTI and underlying comorbidities, were included in the analyses. Comparisons for any UTI, ≥1 hospitalization for UTI, and ≥3 hospitalizations for UTI between the 2 cohorts by following up until 2015 were performed. In both cohorts, the percentages of age subgroups were 65-74 years (65.7%), 75-84 years (30.1%), and ≥85 years (4.2%). The male sex was 42.4%. Patients with OA had an increased risk of any UTI compared with those without OA after adjusting for all past histories (adjusted hazard ratio [AHR]: 1.72; 95% confidence interval [CI]: 1.64-1.80). Compared with patients without OA, patients with OA also had an increased risk of ≥1 hospitalization for UTI and ≥3 hospitalizations for UTI (AHR: 1.13; 95% CI: 1.06-1.19 and AHR: 1.25; 95% CI: 1.13-1.38, respectively). In addition to OA, age 75-84 years, female sex, history of UTI, benign prostatic hyperplasia, indwelling urinary catheter, cerebrovascular disease, dementia, and urolithiasis were independent predictors for any UTI. This study showed that OA was associated with UTI in older adults. We suggest appropriately managing OA and controlling underlying comorbidities to prevent subsequent UTI.

Urinary Symptoms and Bladder Voiding Dysfunction Are Common in Young Men with Defecatory Disorders: A Retrospective Evaluation

BACKGROUND AND AIMS

Lower urinary tract symptoms (LUTS) are frequently reported by constipated patients. Prospective studies investigating the association between defecatory disorders (DDs) and voiding dysfunction, predominantly in women, have reported conflicting results. This study investigated (1) the prevalence of LUTS in young men with DDs and (2) the association between objectively documented DDs and voiding dysfunction in constipated young men with LUTS.

METHODS

We reviewed the medical records, including validated questionnaires, of men aged 18-40 with confirmed DDs treated with pelvic floor physical therapy (PT) at our institution from May 2018 to November 2020. In a separate group of constipated young men with LUTS who underwent high-resolution anorectal manometry (HRM), rectal balloon expulsion test (BET), and uroflowmetry, we explored the relationship between DDs and voiding dysfunction.

RESULTS

A total of 72 men were evaluated in the study. Among 43 men receiving PT for a proven DD, 82% reported ≥ 1 LUTS, most commonly frequent urination. Over half of these men experienced a reduction in LUTS severity after bowel-directed pelvic floor PT. Among 29 constipated men with LUTS who had undergone HRM/BET and uroflowmetry, 28% had concurrent defecatory and voiding dysfunction, 10% had DD alone, 14% had only voiding dysfunction, and 48% had neither. The presence of DD was associated with significantly increased odds of concurrent voiding dysfunction (odds ratio 9.3 [95% CI 1.7-52.7]).

CONCLUSIONS

Most young men with DDs experience LUTS, which may respond to bowel-directed physical therapy. Patients with DD and urinary symptoms have increased odds of voiding dysfunction.

Lead acetate versus cadmium sulfate in the modulation of main physiological pathways controlling detrusor muscle contractility in rat

Heavy metals have a deleterious effect on lower urinary tract functions. Scant data has been reported about metals’ effect on altering detrusor muscle contractility. Rats were given lead acetate (3, 30 mg/kg), cadmium sulfate (0.1, 1 mg/kg) or ferrous sulfate-iron overload-(3, 30 mg/kg), in a subacute toxicity study (21 days, ip). In-vitro tension experiments were conducted using isolated rat detrusor muscle. Measurement of heavy metal concentrations in blood and tissue homogenates was performed, as well as histopathological examinations. Subacute toxicity induced by treatment with lead and cadmium was manifested as a decrease in EFS, ACh, and ATP-mediated contraction of isolated detrusor muscle. Iron overload only decreased E_MAX of EFS and ACh-mediated contraction. Lead (30 mg/kg) caused an upward shift in the dose response curve of isoprenaline-induced relaxation, with a significant decrease in E_MAX. Lead (30 mg/kg) or cadmium (1 mg/kg) inhibited adenosine (10⁻⁵ M)-induced relaxation. Comparisons to control tissues showed a selective accumulation of metals in the detrusor muscle. Histopathological examinations revealed edema and inflammation in the urinary bladder. Directly added lead (10 mM) inhibited detrusor muscle contraction in-vitro, and its effect was decreased in presence of atropine, and potentiated in presence of TEA, L-NAME, or MB. Cadmium's (0.1 mM) inhibitory effect was reduced in presence of nifedipine or trifluoperazine. In conclusion, lead, cadmium, or iron induce detrusor hypoactivity: The inhibitory effect of lead may be mediated by modulating muscarinic receptors but not the K⁺/NO/cGMP pathway, whereas cadmium inhibitory effect may be mediated by inhibiting the Ca²⁺/calmodulin pathway.

The effect of amino acids on the bladder cycle: a concise review

The human bladder maintains a cycle of filling, storing, and micturating throughout an individual's lifespan. The cycle relies on the ability of the bladder to expand without increasing the intravesical pressure, which is only possible with the controlled relaxation of well-complaint muscles and the congruously organized construction of the bladder wall. A competent bladder outlet, which functions in a synchronous fashion with the bladder, is also necessary for this cycle to be completed successfully without deterioration. In this paper, we aimed to review the contemporary physiological findings on bladder physiology and examine the effects of amino acids on clinical conditions affecting the bladder, with special emphasis on the available therapeutic evidence and possible future roles of the amino acids in the treatment of the bladder-related disorders.

Time-of-day dependent changes in guinea pig bladder afferent mechano-sensitivity

The voiding of urine has a clear circadian rhythm with increased voiding during active phases and decreased voiding during inactive phases. Bladder spinal afferents play a key role in the regulation of bladder storage and voiding, but it is unknown whether they exhibit themselves a potential circadian rhythm. Therefore, this study aimed to determine the mechano- and chemo- sensitivity of three major bladder afferent classes at two opposite day-night time points. Adult female guinea pigs underwent conscious voiding monitoring and bladder ex vivo single unit extracellular afferent recordings at 0300 h and 1500 h to determine day-night modulation of bladder afferent activity. All guinea pigs voided a higher amount of urine at 1500 h compared to 0300 h. This was due to an increased number of voids at 1500 h. The mechano-sensitivity of low- and high-threshold stretch-sensitive muscular-mucosal bladder afferents to mucosal stroking and stretch was significantly higher at 1500 h compared to 0300 h. Low-threshold stretch-insensitive mucosal afferent sensitivity to stroking was significantly higher at 1500 h compared to 0300 h. Further, the chemosensitivity of mucosal afferents to N-Oleoyl Dopamine (endogenous TRPV1 agonist) was also significantly increased at 1500 h compared to 0300 h. This data indicates that bladder afferents exhibit a significant time-of-day dependent variation in mechano-sensitivity which may influence urine voiding patterns. Further studies across a 24 h period are warranted to reveal potential circadian rhythm modulation of bladder afferent activity.

Urothelial Calcium-Sensing Receptor Modulates Micturition Function via Mediating Detrusor Activity and Ameliorates Bladder Hyperactivity in Rats

The urothelium displays mechano- and chemosensory functions via numerous receptors and channels. The calcium-sensing receptor (CaSR) detects extracellular calcium and modulates several physiological functions. Nonetheless, information about the expression and the role of CaSR in lower urinary tract has been absent. We aimed to determine the existence of urothelial CaSR in urinary bladder and its effect on micturition function. We utilized Western blot to confirm the expression of CaSR in bladder and used immunofluorescence to verify the location of the CaSR in the bladder urothelium via colocalization with uroplakin III A. The activation of urothelial CaSR via the CaSR agonist, AC-265347 (AC), decreased urinary bladder smooth muscle (detrusor) activity, whereas its inhibition via the CaSR antagonist, NPS-2143 hydrochloride (NPS), increased detrusor activity in in vitro myography experiments. Cystometry, bladder nerve activities recording, and bladder surface microcirculation detection were conducted to evaluate the effects of the urothelial CaSR via intravesical administrations. Intravesical AC inhibited micturition reflex, bladder afferent and efferent nerve activities, and reversed cystitis-induced bladder hyperactivity. The urothelial CaSR demonstrated a chemosensory function, and modulated micturition reflex via regulating detrusor activity. This study provided further evidence of how the urothelial CaSR mediated micturition and implicated the urothelial CaSR as a potential pharmacotherapeutic target in the intervention of bladder disorders.

Characterization of Urothelial Inclusions in Male Wistar Han Rats Treated Orally With the Novel α2A-Adrenoceptor Agonist Tasipimidine

Intracellular inclusions were observed in urinary bladder epithelium of male Wistar rats, following oral treatment with high doses of the α_2A-adrenoceptor agonist tasipimidine for 28 days. No cell death or inflammation was associated with the brightly eosinophilic inclusions. Electron microscopy (EM) studies showed that the inclusions represented intact or fragmented red blood cells (RBC) resulting from erythrophagocytosis, further supported by the presence of iron in urothelial cells. In addition, scattered iron-positive macrophages were observed in the submucosa and muscle layer, indicating microvascular leakage, as no major hemorrhage was evident. Despite the presence of inclusions, the urothelium showed normal uroplakin III distribution, normal cell turnover, and an absence of α-2u-globulin. It is, therefore, concluded that the inclusions were not associated with urothelial damage or increased renewal of the epithelium. This finding shows also that urothelial cells have the capability to phagocytize and break down RBCs originating from submucosal microvascular leakage. Similar changes were not observed in tasipimidine-treated beagle dogs (28 days), suggesting these findings were rat specific. The leakage of RBCs into the urothelium is suggested to be a consequence of exaggerated pharmacology leading to vasoconstriction of submucosal blood vessels in combination with transient increased bladder distension and pressure.

Lipopolysaccharide reduces urethral smooth muscle contractility via cyclooxygenase activation

Lipopolysaccharide (LPS) is a component of gram-negative bacteria wall that elicits inflammatory response in the host through the toll-like receptor 4 (TLR4) activation. In the lower urinary tract (LUT), bacteria-derived LPS has been associated with lower urinary tract symptoms (LUTS); however, little is known about the effects of LPS in the urethral smooth muscle (USM). In the present study, we evaluated the functional and molecular effects of LPS in mouse USM in vitro, focusing on the LPS-induced TLR4-signaling pathway. Male C57BL6/JUnib and TLR4 knockout mice (TLR4 KO) were used. The USM contraction was performed in the presence of LPS (62.5-500 μg/mL), indomethacin (10 μM), L-NAME (100 μM), and TAK 242 (1 μM). The RT-PCR assay for the IL-1β, NF-kB, and COX-2 genes was also evaluated in the presence of LPS (125 μg/mL) and caspase 1 inhibitor (20 μM). Our results showed that LPS reduces mouse USM contraction elicited by phenylephrine and vasopressin. This LPS-induced urethral inhibitory effect was not reversed by the TLR4 inhibition or its absence in the TLR4 KO mice. Conversely, indomethacin (but not L-NAME) reversed the LPS-induced USM hypocontractility. Molecular protocols indicated upregulation of IL-1β, NF-kβ, and COX-2 mRNA upon LPS incubation, which were blunted by caspase 1 inhibition. Our data showed that LPS reduced mouse USM contraction independently of TLR4 activation, involving caspase 1 and IL1β, NF-kB, and COX-2 gene overexpression. Therefore, this alternative pathway might be a valuable target to reduce the LPS-induced urethral dysfunction under infection and inflammatory conditions.

Assessment of the Grades of Vesicoureteral Reflux in Stented Ureters: An Experimental Study

INTRODUCTION

The aim of this experimental study is to assess, in a porcine model, the onset and grades of vesicoureteral reflux associated with ureteral stents.

METHODS

Twenty-four female porcine models were used. A 4.7-Fr ureteral stent was placed in all right ureters and kept in place for 6 weeks. Follow-ups were performed on weeks 1, 3, 6, and 12. Ultrasonography, cystoscopy, and fluoroscopy were used to analyze grade of hydronephrosis, presence and grade of vesicoureteral reflux, bacteriuria, and macroscopic changes of the ureteral orifices. Vesicoureteral reflux was classified using a modification of the International Reflux Study Committee grades.

RESULTS

91.7% animals present vesicoureteral reflux, 89.5% grade IA, 3.5% grade IB, and 7% grade II. There is a significant increase in reflux during follow-ups at 3 and 6 weeks, whereas 6 weeks after removal, 26.3% of the ureters still present vesicoureteral reflux. Hydronephrosis and macroscopic changes of the ureteral orifice increase significantly with stenting, but there is no significant association between them and vesicoureteral reflux; the relationship between bacteriuria and the presence of vesicoureteral reflux is not significant either.

CONCLUSION

Vesicoureteral reflux caused by ureteral stents in an animal model is mostly low grade and mainly affects the distal ureter.

Role of Ano1 Ca2+-activated Cl- channels in generating urethral tone

Urinary continence is maintained in the lower urinary tract by the contracture of urethral sphincters, including smooth muscle of the internal urethral sphincter. These contractions occlude the urethral lumen, preventing urine leakage from the bladder to the exterior. Over the past 20 years, research on the ionic conductances that contribute to urethral smooth muscle contractility has greatly accelerated. A debate has emerged over the role of interstitial cell of Cajal (ICC)-like cells in the urethra and their expression of Ca²⁺-activated Cl^- channels encoded by anoctamin-1 [Ano1; transmembrane member 16 A (Tmem16a) gene]. It has been proposed that Ano1 channels expressed in urethral ICC serve as a source of depolarization for smooth muscle cells, increasing their excitability and contributing to tone. Although a clear role for Ano1 channels expressed in ICC is evident in other smooth muscle organs, such as the gastrointestinal tract, the role of these channels in the urethra is unclear, owing to differences in the species (rabbit, rat, guinea pig, sheep, and mouse) examined and experimental approaches by different groups. The importance of clarifying this situation is evident as effective targeting of Ano1 channels may lead to new treatments for urinary incontinence. In this review, we summarize the key findings from different species on the role of ICC and Ano1 channels in urethral contractility. Finally, we outline proposals for clarifying this controversial and important topic by addressing how cell-specific optogenetic and inducible cell-specific genetic deletion strategies coupled with advances in Ano1 channel pharmacology may clarify this area in future studies.NEW & NOTEWORTHY Studies from the rabbit have shown that anoctamin-1 (Ano1) channels expressed in urethral interstitial cells of Cajal (ICC) serve as a source of depolarization for smooth muscle cells, increasing excitability and tone. However, the role of urethral Ano1 channels is unclear, owing to differences in the species examined and experimental approaches. We summarize findings from different species on the role of urethral ICC and Ano1 channels in urethral contractility and outline proposals for clarifying this topic using cell-specific optogenetic approaches.

Unexpected case of large ureteric calculus being passed following prostatic artery embolisation

Spontaneous passage of large ureteric calculi over 10mm is uncommon. We present a case of a 69-year-old male with a significant prostatic enlargement (150 cc) and a 13mm ureteric calculus which had not passed for 3 months following a failed attempt at ureteroscopy. His stone passed spontaneously following prostatic artery embolisation (PAE), performed for symptomatic benign prostatic hypertrophy (BPH). We consider the mechanisms by which PAE may impact on the distal ureter which allowed stone passage.

Preoperative exercise interventions to optimize continence outcomes following radical prostatectomy

Urinary incontinence is a common and predictable consequence among men with localized prostate cancer who have undergone radical prostatectomy. Despite advances in the surgical technique, urinary continence recovery time remains variable. A range of surgical and patient-related risk factors contributing to urinary incontinence after radical prostatectomy have been described, including age, BMI, membranous urethral length and urethral sphincter insufficiency. Physical activity interventions incorporating aerobic exercise, resistance training and pelvic floor muscle training programmes can positively influence the return to continence in men after radical prostatectomy. Traditional approaches to improving urinary continence after radical prostatectomy have typically focused on interventions delivered during the postoperative period (rehabilitation). However, the limited efficacy of these postoperative approaches has led to a shift from the traditional reactive model of care to more comprehensive interventions incorporating exercise-based programmes that begin in the preoperative period (prehabilitation) and continue after surgery. Comprehensive prehabilitation interventions include appropriately prescribed aerobic exercise, resistance training and specific pelvic floor muscle instruction and exercise training programmes. Transperineal ultrasonography is a non-invasive and validated method for the visualization of the action of the pelvic floor musculature, providing real-time visual biofeedback to the patient during specific pelvic floor muscle instruction and training. Importantly, the waiting time before surgery can be used for the delivery of comprehensive prehabilitation exercise-based interventions to increase patient preparedness in the lead-up to surgery and optimize continence and health-related quality-of-life outcomes following radical prostatectomy.

The intracellular Ca2+ release channel TRPML1 regulates lower urinary tract smooth muscle contractility

TRPML1 (transient receptor potential mucolipin 1) is a Ca²⁺-permeable, nonselective cation channel that is localized to late endosomes and lysosomes. Here, we investigated the function of TRPML1 channels in regulating lower urinary tract (LUT) smooth muscle cell (SMC) contractility. We found that TRPML1 forms a stable signaling complex with ryanodine receptors (RyRs) in the sarcoplasmic reticulum (SR). We further showed that TRPML1 channels are important for initiating an essential Ca²⁺-signaling negative feedback mechanism between RyRs on SR membranes and K⁺ channels on the plasma membrane. Knockout of TRPML1 channels in mice impaired this pathway, resulting in LUT smooth muscle hypercontractility and symptoms of overactive bladder. Our findings demonstrate a critical role for TRPML1 in LUT function.

TRPML1 (transient receptor potential mucolipin 1) is a Ca²⁺-permeable, nonselective cation channel that is predominantly localized to the membranes of late endosomes and lysosomes (LELs). Intracellular release of Ca²⁺ through TRPML1 is thought to be pivotal for maintenance of intravesicular acidic pH as well as the maturation, fusion, and trafficking of LELs. Interestingly, genetic ablation of TRPML1 in mice (Mcoln1^−/−) induces a hyperdistended/hypertrophic bladder phenotype. Here, we investigated this phenomenon further by exploring an unconventional role for TRPML1 channels in the regulation of Ca²⁺-signaling activity and contractility in bladder and urethral smooth muscle cells (SMCs). Four-dimensional (4D) lattice light-sheet live-cell imaging showed that the majority of LELs in freshly isolated bladder SMCs were essentially immobile. Superresolution microscopy revealed distinct nanoscale colocalization of LEL-expressing TRPML1 channels with ryanodine type 2 receptors (RyR2) in bladder SMCs. Spontaneous intracellular release of Ca²⁺ from the sarcoplasmic reticulum (SR) through RyR2 generates localized elevations of Ca²⁺ (“Ca²⁺ sparks”) that activate plasmalemmal large-conductance Ca²⁺-activated K⁺ (BK) channels, a critical negative feedback mechanism that regulates smooth muscle contractility. This mechanism was impaired in Mcoln1^−/− mice, which showed diminished spontaneous Ca²⁺ sparks and BK channel activity in bladder and urethra SMCs. Additionally, ex vivo contractility experiments showed that loss of Ca²⁺ spark–BK channel signaling in Mcoln1^−/− mice rendered both bladder and urethra smooth muscle hypercontractile. Voiding activity analyses revealed bladder overactivity in Mcoln1^−/− mice. We conclude that TRPML1 is critically important for Ca²⁺ spark signaling, and thus regulation of contractility and function, in lower urinary tract SMCs.

Identification and classification of interstitial cells in the mouse renal pelvis

KEY POINTS

Platelet-derived growth factor receptor-α (PDGFRα) is a novel biomarker along with smooth myosin heavy chain for the pacemaker cells (previously termed 'atypical' smooth muscle cells) in the murine and cynomolgus monkey pelvis-kidney junction. PDGFRα⁺ cells present in adventitial and urothelial layers of murine renal pelvis do not express smooth muscle myosin heavy chain (smMHC) but are in close apposition to nerve fibres. Most c-Kit⁺ cells in the renal pelvis are mast cells. Mast cells (CD117⁺ /CD45⁺ ) are more abundant in the proximal renal pelvis and pelvis-kidney junction regions whereas c-Kit⁺ interstitial cells (CD117⁺ /CD45^- ) are found predominantly in the distal renal pelvis and ureteropelvic junction. PDGFRα⁺ cells are distinct from c-Kit⁺ interstitial cells. A subset of PDGFRα⁺ cells express the Ca²⁺ -activated Cl^- channel, anoctamin-1, across the entire renal pelvis. Spontaneous Ca²⁺ transients were observed in c-Kit⁺ interstitial cells, smMHC⁺ PDGFRα cells and smMHC^- PDGFRα cells using mice expressing genetically encoded Ca²⁺ sensors.

ABSTRACT

Rhythmic contractions of the renal pelvis transport urine from the kidneys into the ureter. Specialized pacemaker cells, termed atypical smooth muscle cells (ASMCs), are thought to drive the peristaltic contractions of typical smooth muscle cells (TSMCs) in the renal pelvis. Interstitial cells (ICs) in close proximity to ASMCs and TSMCs have been described, but the role of these cells is poorly understood. The presence and distributions of platelet-derived growth factor receptor-α⁺ (PDGFRα⁺ ) ICs in the pelvis-kidney junction (PKJ) and distal renal pelvis were evaluated. We found PDGFRα⁺ ICs in the adventitial layers of the pelvis, the muscle layer of the PKJ and the adventitia of the distal pelvis. PDGFRα⁺ ICs were distinct from c-Kit⁺ ICs in the renal pelvis. c-Kit⁺ ICs are a minor population of ICs in murine renal pelvis. The majority of c-Kit⁺ cells were mast cells. PDGFRα⁺ cells in the PKJ co-expressed smooth muscle myosin heavy chain (smMHC) and several other smooth muscle gene transcripts, indicating these cells are ASMCs, and PDGFRα is a novel biomarker for ASMCs. PDGFRα⁺ cells also express Ano1, which encodes a Ca²⁺ -activated Cl^- conductance that serves as a primary pacemaker conductance in ICs of the GI tract. Spontaneous Ca²⁺ transients were observed in c-Kit⁺ ICs, smMHC⁺ PDGFRα cells and smMHC^- PDGFRα cells using genetically encoded Ca²⁺ sensors. A reporter strain of mice with enhanced green fluorescent protein driven by the endogenous promotor for Pdgfra was shown to be a powerful new tool for isolating and characterizing the phenotype and functions of these cells in the renal pelvis.

The Role of Purinergic Receptors in the Circadian System

The circadian system is an internal time-keeping system that synchronizes the behavior and physiology of an organism to the 24 h solar day. The master circadian clock, the suprachiasmatic nucleus (SCN), resides in the hypothalamus. It receives information about the environmental light/dark conditions through the eyes and orchestrates peripheral oscillators. Purinergic signaling is mediated by extracellular purines and pyrimidines that bind to purinergic receptors and regulate multiple body functions. In this review, we highlight the interaction between the circadian system and purinergic signaling to provide a better understanding of rhythmic body functions under physiological and pathological conditions.

Soft Phantom for the Training of Renal Calculi Diagnostics and Lithotripsy

Organ models are important for medical training and surgical planning. With the fast development of additive fabrication technologies, including 3D printing, the fabrication of 3D organ phantoms with precise anatomical features becomes possible. Here, we develop the first high-resolution kidney phantom based on soft material assembly, by combining 3D printing and polymer molding techniques. The phantom exhibits both the detailed anatomy of a human kidney and the elasticity of soft tissues. The phantom assembly can be separated into two parts on the coronal plane, thus large renal calculi are readily placed at any desired location of the calyx. With our sealing method, the assembled phantom withstands a hydraulic pressure that is four times the normal intrarenal pressure, thus it allows the simulation of medical procedures under realistic pressure conditions. The medical diagnostics of the renal calculi is performed by multiple imaging modalities, including X-ray, ultrasound imaging and endoscopy. The endoscopic lithotripsy is also successfully performed on the phantom. The use of a multifunctional soft phantom assembly thus shows great promise for the simulation of minimally invasive medical procedures under realistic conditions.

Contribution of Cav1.2 Ca2+ channels and store-operated Ca2+ entry to pig urethral smooth muscle contraction

Urethral smooth muscle (USM) generates tone to prevent urine leakage from the bladder during filling. USM tone has been thought to be a voltage-dependent process, relying on Ca²⁺ influx via voltage-dependent Ca²⁺ channels in USM cells, modulated by the activation of Ca²⁺-activated Cl^- channels encoded by Ano1. However, recent findings in the mouse have suggested that USM tone is voltage independent, relying on Ca²⁺ influx through Orai channels via store-operated Ca²⁺ entry (SOCE). We explored if this pathway also occurred in the pig using isometric tension recordings of USM tone. Pig USM strips generated myogenic tone, which was nearly abolished by the Ca_v1.2 channel antagonist nifedipine and the ATP-dependent K⁺ channel agonist pinacidil. Pig USM tone was reduced by the Orai channel blocker GSK-7975A. Electrical field stimulation (EFS) led to phentolamine-sensitive contractions of USM strips. Contractions of pig USM were also induced by phenylephrine. Phenylephrine-evoked and EFS-evoked contractions of pig USM were reduced by ~50-75% by nifedipine and ~30% by GSK-7975A. Inhibition of Ano1 channels had no effect on tone or EFS-evoked contractions of pig USM. In conclusion, unlike the mouse, pig USM exhibited voltage-dependent tone and agonist/EFS-evoked contractions. Whereas SOCE plays a role in generating tone and agonist/neural-evoked contractions in both species, this dominates in the mouse. Tone and agonist/EFS-evoked contractions of pig USM are the result of Ca²⁺ influx primarily through Ca_v1.2 channels, and no evidence was found supporting a role of Ano1 channels in modulating these mechanisms.

Uroflowmetry and Altitude Hypoxia: A Report from Healthy Italian Trekkers and Nepali Porters During Himalayan Expedition

Hypoxia alters micturition, which influences bladder function by involving different neurological and humoral systems. In this study we assessed the mid-term effects of altitude hypoxia on uroflowmetry in healthy male lowlander native Nepali porters and Italian trekkers, four each, who coattended a Himalayan expedition. All the participants completed a 19-day trek along a demanding route with ascent and descent at the Kanchenjunga Mountain. They underwent micturition and urodynamic analysis twice, at low altitude of 665 m a.s.l. and high altitude of 4,750 m a.s.l. Statistical comparisons considered the altitude effects (low vs. high) and ethnicity (Italian vs. Nepali). Food consumption was recorded, and water and energy intake were calculated. We found trends of borderline significance in the mean urinary flow rate (Q_mean) (p = 0.058; effect size η² p = 0.478) and in Q_max to the advantage of the Nepali. There was no evidence of differences when comparing time to Q_max and urine volume at Q_max and Q_mean for altitude or altitude × ethnicity. In addition, there was a lonely female participant, who, analyzed as a case report, showed increased Q_mean at high altitude. Older age mitigated while energy intake potentiated the ethnic differences noted in uroflowmetry. We conclude that altitude hypoxia rather inappreciably affects micturition in healthy men. However, a trend for possible ethnic differences raises worthy of note perspectives on adaptive ability of micturition. Also, dietary intake and age should be considered as confounding elements when evaluating micturition.

Urinary physiology and hypoxia: a pilot study of moderate-altitude trekking effects on urodynamic indexes

Exposure to high altitude is one of the most widely used models to study the adaptive response to hypoxia in humans. However, little is known about the related effects on micturition. The present study addresses the adaptive urinary responses in four healthy adult lowlanders, comparing urodynamic indexes at Kathmandu [1,450 m above sea level (a.s.l.); K1450] and during a sojourn in Namche Bazar (3,500 m a.s.l.; NB3500). The urodynamic testing consisted of cistomanometry and bladder pressure/flow measurements. Anthropometrics, electrocardiographic, and peripheral capillary oxygen saturation data were also collected. The main findings consisted of significant reductions in bladder power at maximum urine flow by ~30%, bladder contractility index by 13%, and infused volume both at first (by 57%) and urgency sensation (by 14%) to urinate, indicating a reduced cystometric capacity, at NB3500. In addition to the urinary changes, we found that oxygen saturation, body mass index, body surface area, and median RR time were all significantly reduced at altitude. We submit that the hypoxia-related parasympathetic inhibition could be the underlying mechanism of both urodynamic and heart rate adaptive responses to high-altitude exposure. Moreover, increased diuresis and faster bladder filling at altitude may trigger the anticipation of being able to void, a common cause of urgency. We believe that the present pilot study represents an original approach to the study of urinary physiology at altitude.

Doxorubicin induces detrusor smooth muscle impairments through myosin dysregulation, leading to a risk of lower urinary tract dysfunction

Cytotoxic chemotherapy is the foundation for the treatment of the wide variety of childhood malignancies; however, these therapies are known to have a variety of deleterious side effects. One common chemotherapy used in children, doxorubicin (DOX), is well known to cause cardiotoxicity and cardiomyopathy. Recent studies have revealed that DOX impairs skeletal and smooth muscle function and contributes to fatigue and abnormal intestinal motility in patients. In this study, we tested the hypothesis that systemic DOX administration also affects detrusor smooth muscle (DSM) function in the urinary bladder, especially when administered at a young age. The effects on the DSM and bladder function were assessed in BALB/cJ mice that received six weekly intravenous injections of DOX (3 mg·kg^-1·wk^-1) or saline for the control group. Systemic DOX administration resulted in DSM hypertrophy, increased voiding frequency, and a significant attenuation of DSM contractility, followed by a slower relaxation compared with the control group. Gene expression analyses revealed that unlike DOX-induced cardiotoxicity, the bladders from DOX-administered animals showed no changes in oxidative stress markers; instead, downregulation of large-conductance Ca²⁺-activated K⁺ channels and altered expression of myosin light-chain kinase coincided with reduced myosin light-chain phosphorylation. These results indicate that in vivo DOX exposure caused DSM dysfunction by dysregulation of molecules involved in the detrusor contractile-relaxation mechanisms. Collectively, our findings suggest that survivors of childhood cancer treated with DOX may be at increased risk of bladder dysfunction and benefit from followup surveillance of bladder function.

A Review of Botulinum Toxin A for the Treatment of Neurogenic Bladder

Prior to FDA approval of intradetrusor botulinum toxin (BoTA) injections for the treatment of neurogenic bladder, patients' treatment options were limited to use of pharmacotherapies such as antimuscarinics, alpha blockers, and more recently beta agonists (some off-label) or invasive interventions including bladder augmentation and urinary diversion procedures. Herein, we provide a comprehensive literature review detailing the salient clinical literature that led to FDA approval of intradetrusor BoTA for neurogenic bladder. Patients with neurogenic detrusor overactivity and detrusor sphincter dyssynergia have been shown in randomized studies to benefit significantly from intradetrusor BoTA injection with regard to the following parameters: improved voided volume, improved bladder pressure and urodynamic parameters, reduced incidence of urinary tract infection, and improved quality of life. Intradetrusor BoTA injection has revolutionized the treatment landscape for patients with neurogenic bladder by providing them with a safe, efficacious, and cost-effective means to reduce bladder dysfunction, preserve renal function, and reduce the need for invasive, surgical intervention. LEVEL OF EVIDENCE: I.

Influence of barbed suture on leak pressures after double-layer inverting closure of cystotomy sites in sheep

OBJECTIVE

To determine the influence of barbed suture on double-layer inverting closure of cystotomy sites in sheep.

STUDY DESIGN

Ex vivo study.

SAMPLE POPULATION

Urinary bladders harvested from ovine (n = 26) cadaveric specimens.

METHODS

After collection and specimen preparation, a 3-cm-long incision was created on the ventral aspect of the urinary bladder. The cystotomy was repaired with barbed (n = 13) or nonbarbed analogous monofilament absorbable suture (n = 13) in a double-layer inverting suture pattern. Time required for closure in seconds was recorded for each test. Each bladder was connected to a pressure transducer to monitor intraluminal pressure during infusion with dyed Hartmann's solution until leakage occurred. Intraluminal pressure at time of initial leakage and leakage site were also recorded. Two-sample t tests were used to compare initial leakage pressure and closure time between the 2 types of suture (P = .05).

RESULTS

The mean ( ± SD) leakage pressure of ovine urinary bladder incisions did not differ between closures with barbed sutures (42.3 ± 21.7 mmHg) and nonbarbed closures (32.5 ± 14.4 mmHg, P = .187). Cystorrhaphies were performed faster with barbed suture (307 ± 50 seconds) than with nonbarbed suture (390 ± 62 seconds, P = .001).

CONCLUSION

The use of barbed suture did not affect mean leakage pressure of ovine urinary bladder incisions but decreased the time required to complete cystorrhaphies in this model.

CLINICAL SIGNIFICANCE

This study provides evidence to support the use of knotless barbed suture for open ovine cystorrhaphies. Use of such suture for laparoscopic and laparoscopic-assisted procedures in sheep warrants caution until cyclic and in vivo testing is performed with appropriate laparoscopic instrumentation.

The efficacy of mirabegron in the treatment of urgency and the potential utility of combination therapy

Urgency is the prevalent and most bothersome symptom of overactive bladder (OAB) and the treatment of urgency is the primary objective in the management of OAB. Urgency has a major impact on other symptoms of OAB and culminates in an increased frequency of micturition and reduced volume voided, which may contribute to shorter intervals between the need to void. Antimuscarinic agents and mirabegron, a β3-adrenoceptor agonist, constitute the main oral pharmacotherapeutic options for the treatment of urgency and other OAB symptoms. The reduction of urgency and other OAB symptoms significantly improve health-related quality of life. This review will explore the distinct mechanisms of action and effects of antimuscarinic agents and mirabegron, in relation to their effect on the pathophysiology of urgency. The review will also provide an overview of the various validated measurements of urgency and the numerous clinical trials regarding antimuscarinic agent monotherapy, mirabegron monotherapy, or combination treatment with mirabegron added on to the antimuscarinic agent solifenacin. A narrative review of the literature relating to pathophysiology of urgency, the validated measurements of urgency, and clinical trials relating to the pharmacological treatment of urgency. Antimuscarinic agent monotherapy, mirabegron monotherapy, or combination treatment with mirabegron added on to the antimuscarinic agent solifenacin statistically significantly reduce the symptoms of urgency compared with placebo. Combination therapy with mirabegron added on to solifenacin also statistically significantly reduces the symptoms of severe urgency compared with antimuscarinic agent monotherapy. A critique of the clinical benefits of combination therapy is also provided. Combination therapy provides an alternative treatment in patients with OAB that includes urgency who respond poorly to first-line monotherapy and who may otherwise often move on to more invasive treatments.

Laboratory practical to study the differential innervation pathways of urinary tract smooth muscle

In the mammalian lower urinary tract, there is a reciprocal relationship between the contractile state of the bladder and urethra. As the bladder fills with urine, it remains relaxed to accommodate increases in volume, while the urethra remains contracted to prevent leakage of urine from the bladder to the exterior. Disruptions to the normal contractile state of the bladder and urethra can lead to abnormal micturition patterns and urinary incontinence. While both the bladder and urethra are smooth-muscle organs, they are differentially contracted by input from cholinergic and sympathetic nerves, respectively. The laboratory practical described here provides an experiential approach to understanding the anatomy of the lower urinary tract. Several key factors in urinary tract physiology are outlined, e.g., the bladder is contracted by activation of the parasympathetic pathway via cholinergic stimulation on muscarinic receptors, whereas the urethra is contracted by activation of the sympathetic pathway via adrenergic stimulation on α₁-adrenoceptors. This is achieved by measuring the force generated by bladder and urethra smooth muscle to demonstrate that acetylcholine contracts the smooth muscle of the bladder, whereas adrenergic agonists contract the urethral smooth muscle. An inhibition of these effects is also demonstrated by application of the muscarinic receptor antagonist atropine and the α₁-adrenergic receptor blocker phentolamine. A list of suggested techniques and exam questions to evaluate student understanding on this topic is also provided.

Toward Self-Control Systems for Neurogenic Underactive Bladder: A Triboelectric Nanogenerator Sensor Integrated with a Bistable Micro-Actuator

Aging, neurologic diseases, and diabetes are a few risk factors that may lead to underactive bladder (UAB) syndrome. Despite all of the serious consequences of UAB, current solutions, the most common being ureteric catheterization, are all accompanied by serious shortcomings. The necessity of multiple catheterizations per day for a physically able patient not only reduces the quality of life with constant discomfort and pain but also can end up causing serious complications. Here, we present a bistable actuator to empty the bladder by incorporating shape memory alloy components integrated on flexible polyvinyl chloride sheets. The introduction of two compression and restoration phases for the actuator allows for repeated actuation for a more complete voiding of the bladder. The proposed actuator exhibits one of the highest reported voiding percentages of up to 78% of the bladder volume in an anesthetized rat after only 20 s of actuation. This amount of voiding is comparable to the common catheterization method, and its one time implantation onto the bladder rectifies the drawbacks of multiple catheterizations per day. Furthermore, the scaling of the device for animal models larger than rats can be easily achieved by adjusting the number of nitinol springs. For neurogenic UAB patients with degraded nerve function as well as degenerated detrusor muscle, we integrate a flexible triboelectric nanogenerator sensor with the actuator to detect the fullness of the bladder. The sensitivity of this sensor to the filling status of the bladder shows its capability for defining a self-control system in the future that would allow autonomous micturition.

Ca2+ signalling in mouse urethral smooth muscle in situ: role of Ca2+ stores and Ca2+ influx mechanisms

KEY POINTS

Contraction of urethral smooth muscle cells (USMCs) contributes to urinary continence. Ca2+ signalling in USMCs was investigated in intact urethral muscles using a genetically encoded Ca2+ sensor, GCaMP3, expressed selectively in USMCs. USMCs were spontaneously active in situ, firing intracellular Ca2+ waves that were asynchronous at different sites within cells and between adjacent cells. Spontaneous Ca2+ waves in USMCs were myogenic but enhanced by adrenergic or purinergic agonists and decreased by nitric oxide. Ca2+ waves arose from inositol trisphosphate type 1 receptors and ryanodine receptors, and Ca2+ influx by store-operated calcium entry was required to maintain Ca2+ release events. Ca2+ release and development of Ca2+ waves appear to be the primary source of Ca2+ for excitation-contraction coupling in the mouse urethra, and no evidence was found that voltage-dependent Ca2+ entry via L-type or T-type channels was required for responses to α adrenergic responses.

ABSTRACT

Urethral smooth muscle cells (USMCs) generate myogenic tone and contribute to urinary continence. Currently, little is known about Ca2+ signalling in USMCs in situ, and therefore little is known about the source(s) of Ca2+ required for excitation-contraction coupling. We characterized Ca2+ signalling in USMCs within intact urethral muscles using a genetically encoded Ca2+ sensor, GCaMP3, expressed selectively in USMCs. USMCs fired spontaneous intracellular Ca2+ waves that did not propagate cell-to-cell across muscle bundles. Ca2+ waves increased dramatically in response to the α1 adrenoceptor agonist phenylephrine (10 μm) and to ATP (10 μm). Ca2+ waves were inhibited by the nitric oxide donor DEA NONOate (10 μm). Ca2+ influx and release from sarcoplasmic reticulum stores contributed to Ca2+ waves, as Ca2+ free bathing solution and blocking the sarcoplasmic Ca2+ -ATPase abolished activity. Intracellular Ca2+ release involved cooperation between ryanadine receptors and inositol trisphosphate receptors, as tetracaine and ryanodine (100 μm) and xestospongin C (1 μm) reduced Ca2+ waves. Ca2+ waves were insensitive to L-type Ca2+ channel modulators nifedipine (1 μm), nicardipine (1 μm), isradipine (1 μm) and FPL 64176 (1 μm), and were unaffected by the T-type Ca2+ channel antagonists NNC-550396 (1 μm) and TTA-A2 (1 μm). Ca2+ waves were reduced by the store operated Ca2+ entry blocker SKF 96365 (10 μm) and by an Orai antagonist, GSK-7975A (1 μm). The latter also reduced urethral contractions induced by phenylephrine, suggesting that Orai can function effectively as a receptor-operated channel. In conclusion, Ca2+ waves in mouse USMCs are a source of Ca2+ for excitation-contraction coupling in urethral muscles.

A 3D Printed Implantable Device for Voiding the Bladder Using Shape Memory Alloy (SMA) Actuators

Underactive bladder or detrusor underactivity (DU) is defined as a reduction of contraction strength or duration of the bladder wall. Despite the serious healthcare implications of DU, there are limited solutions for affected individuals. A flexible 3D printed implantable device driven by shape memory alloys (SMA) actuators is presented here for the first time to physically contract the bladder to restore voluntary control of the bladder for individuals suffering from DU. This approach is used initially in benchtop experiments with a rubber balloon acting as a model for the rat bladder to verify its potential for voiding, and that the operating temperatures are safe for the eventual implantation of the device in a rat. The device is then implanted and tested on an anesthetized rat, and a voiding volume of more than 8% is successfully achieved for the SMA-based device without any surgical intervention or drug injection to relax the external sphincter.

Cystometrogram: the low-cost method for rural areas and its benefits

Cystometrography (CMG) is a means of studying bladder pressure. It is a very useful diagnostic tool in patients with lower urinary tract symptoms for which a simple cystoscopy will not offer sufficient information to form a diagnosis. Of the 8893 patients who underwent screening for urological conditions in rural northeast India during 2010-2014, 280 with lower urinary tract symptoms were investigated with a combination of cystoscopy and CMG. By corresponding CMG diagnosis and treatment, we could examine patients' overall satisfaction with both the procedure and the treatment. We describe a low-cost method of CMG and our results using this method in rural areas of India.

Octodon degus, a new model to study the agonist and plexus-induced response in the urinary bladder

Urinary bladder function consists in the storage and controlled voiding of urine. Translational studies require animal models that match human characteristics, such as Octodon degus, a diurnal rodent. This study aims to characterize the contractility of the detrusor muscle and the morphology and code of the vesical plexus from O. degus. Body temperature was measured by an intra-abdominal sensor, the contractility of detrusor strips was evaluated by isometric tension recording, and the vesical plexus was studied by electrical field stimulation (EFS) and immunofluorescence. The animals showed a diurnal chronotype as judged from core temperature. The myogenic contractile response of the detrusor muscle to increasing doses of KCl reached its maximum (31.04 mN/mm²) at 60 mM. In the case of cumulative dose-response of bethanecol, the maximum response (37.42 mN/mm²) was reached at 3.2 × 10^-4 M. The response to ATP was clearly smaller (3.8 mN/mm²). The pharmacological dissection of the EFS-induced contraction identified ACh and sensory fibers as the main contributors to this response. The neurons of the vesical plexus were located mainly in the trigone area, grouped in big and small ganglia. Out of them, 48.1 % of the neurons were nitrergic and 62.7 % cholinergic. Our results show functional and morphological similarities between the urinary bladder of O. degus and that of humans.

The influence of altitude hypoxia on uroflowmetry parameters in women

There is scientific evidence to suggest a correlation between hypoxia and the physiology of micturition. During a Himalayan Scientific and Mountaineering Expedition, we performed tests to investigate the functional interactions between altitude hypoxia and uroflowmetry parameters in women. The tests were carried out in seven women (36.3 ± 7.1 yr) from normoxic [1,340 meters above sea level (m a.s.l.)] to hypoxic conditions (up to 5,050 m a.s.l.) and during the return descent. The following measures were determined: uroflowmetry parameters and saturation of peripheral oxygen (SpO2). As expected, SpO2 decreased from 97.7 to 77.8% with increasing altitude. Micturition flow time, flow volume, and voiding time increased with altitude ( P < 0.04 for all), indicating a negative correlation with SpO2. In conclusion, in young adult women, micturition physiological parameters were affected during adaptation to hypoxia; the correlation with SpO2 strongly suggests a role of hypoxia in these changes. These data could help to support the design of new strategies for both prevention and medical treatment. An example of the latter might be hyperbaric oxygen therapy, which in some studies has proved able to reduce the symptoms in patients with hypoxic bladder.

Constitutively active PKA regulates neuronal acetylcholine release and contractility of guinea pig urinary bladder smooth muscle

Autonomic and somatic motor neurons that innervate the urinary bladder and urethra control the highly coordinated functions of the lower urinary tract, the storage, and the emptying of urine. ACh is the primary excitatory neurotransmitter in the bladder. Here, we aimed to determine whether PKA regulates neuronal ACh release and related nerve-evoked detrusor smooth muscle (DSM) contractions in the guinea pig urinary bladder. Isometric DSM tension recordings were used to measure spontaneous phasic and electrical field stimulation (EFS)- and carbachol-induced DSM contractions with a combination of pharmacological tools. The colorimetric method was used to measure ACh released by the parasympathetic nerves in DSM isolated strips. The pharmacological inhibition of PKA with H-89 (10 μM) increased the spontaneous phasic contractions, whereas it attenuated the EFS-induced DSM contractions. Intriguingly, H-89 (10 μM) attenuated the (primary) cholinergic component, whereas it simultaneously increased the (secondary) purinergic component of the nerve-evoked contractions in DSM isolated strips. The acetylcholinesterase inhibitor, eserine (10 μM), increased EFS-induced DSM contractions, and the subsequent addition of H-89 attenuated the contractions. H-89 (10 μM) significantly increased DSM phasic contractions induced by the cholinergic agonist carbachol. The inhibition of PKA decreased the neuronal release of ACh in DSM tissues. This study revealed that PKA-mediated signaling pathways differentially regulate nerve-evoked and spontaneous phasic contractions of guinea pig DSM. Constitutively active PKA in the bladder nerves controls synaptic ACh release, thus regulating the nerve-evoked DSM contractions, whereas PKA in DSM cells controls the spontaneous phasic contractility.

Activation of cannabinoid receptor 1 inhibits increased bladder activity induced by nerve growth factor

Nerve growth factor (NGF) is an important mediator of inflammatory pain, in part by sensitizing afferent nerve fibers, and expression of NGF is increased during bladder inflammation. We investigated whether intravesical instillation of the selective cannabinoid receptor 1 (CB1) agonist arachidonyl-2'-chloroethylamide (ACEA) affects NGF-induced increased bladder activity in female C57BL/6J wild-type (WT) mice. We also examined the effects of intravesical NGF in female fatty acid amide hydrolase knock-out (FAAH KO) mice. We found that CB1 and tyrosine kinase A (trkA, the high-affinity NGF receptor) were present in L6 dorsal root ganglion (DRG) afferent neurons and in bladders of both genotypes. Intravesical NGF increased bladder activity that was inhibited by intravesical ACEA in WT mice. The inhibitory effects of ACEA were reversed by the selective CB1 antagonist AM 251. Intravesical NGF failed to affect bladder activity in FAAH KO mice, and treatment with AM251, restored the stimulatory effects of NGF on the bladder in FAAH KO mice. These results indicate that activation of CB1 inhibits increased bladder activity induced by NGF.

Attenuation of cystitis and pain sensation in mice lacking fatty acid amide hydrolase

Endocannabinoids, such as N-arachidonoylethanolamine (AEA, also called anandamide), exert potent analgesic and anti-inflammatory effects. Fatty acid amide hydrolase (FAAH) is primarily responsible for degradation of AEA, and deletion of FAAH increases AEA content in various tissues. Since FAAH has been shown to be present in the bladder of various species, we compared bladder function, severity of experimental cystitis, and cystitis-associated referred hyperalgesia in male wild-type (WT) and FAAH knock-out (KO) mice. Basal concentrations of AEA were greater, and the severity of cyclophosphamide (CYP)-induced cystitis was reduced in bladders from FAAH KO compared to WT mice. Cystitis-associated increased peripheral sensitivity to mechanical stimuli and enhanced bladder activity (as reflected by increased voiding frequency) were attenuated in FAAH KO compared to WT mice. Further, abundances of mRNA for several pro-inflammatory compounds were increased in the bladder mucosa after CYP treatment of WT mice, and this increase was inhibited in FAAH KO mice. These data indicate that endogenous substrates of FAAH, including the cannabinoid AEA, play an inhibitory role in bladder inflammation and subsequent changes in pain perception. Therefore, FAAH could be a therapeutic target to treat clinical symptoms of painful inflammatory bladder diseases.