Bladder Function In Rats Research Articles

531 - Role of corticotropin-releasing factor on bladder function in rats with psychological stress

531 - Role of corticotropin-releasing factor on bladder function in rats with psychological stress

Bladder decompensation and reduction in nerve density in a rat model of chronic bladder outlet obstruction are attenuated with the NLRP3 inhibitor glyburide.

Bladder outlet obstruction (BOO) leads to progressive voiding dysfunction. Acutely, obstruction triggers inflammation that drives bladder dysfunction. Over time, inflammation leads to decreased bladder nerve density and increased fibrosis, responsible for eventual decompensation and irreversibility. We have previously shown that BOO triggers inflammation, reduced bladder nerve density and increased fibrosis via activation of the NLRP3 inflammasome in an acutely obstructed (12-day) rat model. However, as BOO progresses, the bladder may become decompensated with an increase in postvoid residual volume and decreased voiding efficiency. Currently, we have examined rat bladder function and nerve densities after chronic BOO to determine whether NLRP3 plays a role in the decompensation at this stage. Four groups were examined: control, sham-operated, BOO, or BOO+gly (glyburide; an NLRP3 inhibitor). After 42 days, bladder weight, inflammation (Evans blue), urodynamics, and nerve density were measured. BOO greatly enhanced bladder weights and inflammation, while inflammation was prevented by glyburide. Voiding pressures were increased, and flow rates decreased in BOO and BOO+gly groups, demonstrating physical obstruction. No difference in frequency or voided volume was detected. However, postvoid residual volumes were greatly increased in BOO rats while BOO+gly rats were not different than controls. Moreover, there was a dramatic decrease in voiding efficiency in the chronic BOO rats, which was prevented with glyburide treatment. Finally, a reduction in nerve density was apparent with BOO and attenuated with glyburide. Together the results suggest a critical role for NLRP3 in mediating bladder decompensation and nerve density during chronic BOO.

MP09-16 PHARMACOLOGICAL INHIBITION OF THE NLRP3 INFLAMMASOME PREVENTS BLADDER DECOMPENSATION IN A RAT MODEL OF CHRONIC BLADDER OUTLET OBSTRUCTION

You have accessJournal of UrologyBladder & Urethra: Anatomy, Physiology & Pharmacology I1 Apr 2018MP09-16 PHARMACOLOGICAL INHIBITION OF THE NLRP3 INFLAMMASOME PREVENTS BLADDER DECOMPENSATION IN A RAT MODEL OF CHRONIC BLADDER OUTLET OBSTRUCTION Francis Hughes, Stephanie Sexton, Patrick Leidig, Huixia Jin, and J. Purves Francis HughesFrancis Hughes More articles by this author , Stephanie SextonStephanie Sexton More articles by this author , Patrick LeidigPatrick Leidig More articles by this author , Huixia JinHuixia Jin More articles by this author , and J. PurvesJ. Purves More articles by this author View All Author Informationhttps://doi.org/10.1016/j.juro.2018.02.342AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookTwitterLinked InEmail INTRODUCTION AND OBJECTIVES Bladder outlet obstruction (BOO), most often the result of benign prostatic hyperplasia, may lead to progressive voiding dysfunction. BOO can create an overactive bladder (OAB) phenotype defined by increased frequency of voiding and decreased voiding volume (VV)). We have previously shown in the rat that acute BOO (12 days) activates the NLRP3 inflammasome which mediates inflammation and the OAB phenotype. Initially, the bladder can compensate for the obstruction by generating higher voiding pressures. However, over time the bladder decompensates which results in an increase in post-void residual volume (PVR) and decreased voiding efficiency. In this study we have examined the role of NLRP3 on rat bladder function after chronic BOO (42 days) and investigated the utility of an NLRP3 inhibitor in preventing decompensation. METHODS 4 groups were examined: 1) control, 2) sham-operated, 3) BOO and 4) BOO + gly (glyburide; an NLRP3 inhibitor). BOO was created by inserting a 1 mm transurethral catheter, tying a suture around the urethra, and removing the catheter. Gly was provided via 50 mg, 21 day release pellet (s.c.) that was replaced after 21 days. Suprapubic tubes were implanted on Day 35 and urodynamics performed on Day 42. PVR was assessed immediately after the final micturition by drawing back on the catheter with a syringe. The rat was immediately sacrificed and any additional post void liquid remaining in the bladder removed by needle puncture and added to the total PVR volume. RESULTS Voiding pressures were increased and flow rates decreased in BOO and BOO + gly groups, demonstrating physical obstruction of the urethra. No difference in frequency or VV were detected among groups. However, PVRs were greatly increased in BOO rats while BOO + gly rats were not different than controls (Figure 1). Moreover, also shown in Figure 1, there was a dramatic decrease in voiding efficiency in the chronically obstructed rats which was completely prevented by glyburide treatment. CONCLUSIONS The results suggest a critical role for NLRP3 in the progression to bladder decompensation during chronic BOO and that treatment with an NLRP3 inhibitor preserves voiding efficiency. © 2018FiguresReferencesRelatedDetails Volume 199Issue 4SApril 2018Page: e112-e113 Advertisement Copyright & Permissions© 2018MetricsAuthor Information Francis Hughes More articles by this author Stephanie Sexton More articles by this author Patrick Leidig More articles by this author Huixia Jin More articles by this author J. Purves More articles by this author Expand All Advertisement Advertisement PDF downloadLoading ...

Role of Piezo Channels in Urothelial Cell Mechanotransduction

During the micturition cycle, the ability to sense and transduce the degree of tension in the wall of the bladder allows the bladder to accommodate to changing urine volumes and to transmit the filling state to the CNS. The urothelium, and in particular the umbrella cells (UC), is proposed to play an important role in mechanotransduction: upon bladder filling, UC sense membrane stretch and transduce it into a number of cellular responses, including exocytosis of subapical discoidal/fusiform vesicles and release of neurotransmitters. The mechanosensor present in the UC that directly responds to membrane stretch is unknown. Piezo channels are a newly discovered family of mechanosensitive channels associated with the physiological responses to pressure, shear stress and tension. In this study, we sought to determine the involvement of Piezo channels in UC mechanosensation. We found that rat UC express both Piezo1 and Piezo2 channels which exhibit different subcellular localizations: Piezo1 is expressed at the apical region and at tight junction sites, whereas Piezo2 is found in the cytosol. Silencing Piezo1 expression by in-situ transduction of rat bladders with adenoviruses encoding Piezo1-shRNA showed a significant decrease in apical exocytosis (61 ± 9 %) compared to control upon ex vivo bladder filling. We also assessed the impact of knocking-down Piezo1 in bladder function by monitoring continuously the intravesical pressure on anesthetized rats previously transduced with either scrambled- or Piezo1-shRNA. We observed that loss of Piezo1 leads to a lower voiding frequency and also affects bladder compliance (defined as ΔV/ΔP during filling). All together, these results show the involvement of Piezo1 in sensing mechanical stretch required for normal bladder function. Future directions involve establishing the role of Piezo2 in rat bladder function as well as detailed characterization of the cascade of events triggered by Piezo1 activation.

Effects of varying degrees of partial bladder outlet obstruction on urinary bladder function of rats: A novel link to inflammation, oxidative stress and hypoxia.

The aim of the present study was to investigate the effects of different degrees of obstruction, and the roles of inflammation, oxidative stress, and hypoxia parameters on bladder function. Thirty male Sprague-Dawley rats were divided into 3 groups (n = 10 in each group): (i) sham-operated control; (ii) severe partial bladder outlet obstruction (PBOO); and (iii) moderate PBOO. Severe and moderate PBOO were induced by urethral ligation using 3-Fr and 4-Fr catheters, respectively, for 6 weeks. After 6 weeks, the in vitro contractile responses to carbachol, electrical field stimulation, ATP and KCl were measured in bladder strips. In addition, mRNA and protein expression of nuclear factor kappa B (NF-κB) hypoxia-inducible factor (HIF) and nuclear factor, erythroid 2-like 2 (Nrf2) in bladder were determined by real-time polymerase chain reaction and western blotting. Malondialdehyde (MDA) levels in bladder tissues were also determined. Rats in the severe PBOO group had the highest bladder weight. Detrusor strips from rats in the severe PBOO group exhibited 61%-82% smaller contractile responses to all four stimuli than those from the sham-operated group. Activity of NF-κB as an inflammatory marker was increased in the severe PBOO group, whereas HIF-1α and HIF-2β protein levels were increased significantly in the moderate PBOO group. A master regulator of oxidative stress, Nrf2 expression was increased in all obstructed rats. MDA levels were higher in the severe PBOO group than in sham-operated group. The results of the present study reveal the importance of oxidative stress-induced NF-κB signaling in bladder dysfunction with severe obstruction. Altered HIF signaling may contribute to the functional impairment after PBOO. Novel and evolving therapies targeting oxidative and/or inflammatory pathways may be a reasonable strategy for the management of lower urinary tract symptoms or benign prostatic hyperplasia.

Urodynamic measurements reflect physiological bladder function in rats.

Our objective was to investigate and compare bladder function in rats assessed by metabolic cage and by urodynamic measurements in fully awake animals. Bladder function of female Lewis rats was investigated in naïve animals by metabolic cage at baseline, 14-16 days after bladder catheter and external urethral sphincter electromyography electrode implantation in fully awake animals by urodynamics, and again by metabolic cage. Investigating the same animals (n = 8), voided volume, average flow, and duration of voiding were similar (P > 0.05) in naïve animals measured by metabolic cage and after catheter implantation by urodynamic measurements and by metabolic cage. In naïve animals measured by metabolic cage, voided volumes were significantly different in the light (resting phase) versus the dark (active phase) part of the 24 h cycle (mean difference 0.14 mL, 21%, P = 0.004, n = 27). Lower urinary tract function assessed by metabolic cage or by urodynamic meaurements in fully awake rats was indistinguishable. Thus, catheter implantation did not significantly change physiological bladder function. This shows that urodynamic measurements in awake animals are an appropriate approach to study lower urinary tract function in health and disease in animal models, directly paralleling the human diagnostic procedures.

Effect of Suo Quan Wan on the bladder function of aging rats based on the β-adrenoceptor.

Suo Quan Wan (SQW) has been used to treat lower urinary tract symptoms (LUTS) in elderly patients for hundreds of years in China. β-adrenoceptors (β-ARs), particularly β3-adrenoceptor (β3-AR), was reported to be important in the bladder dysfunction of the elderly. The present study was conducted to explore the effect of β-AR, and particularly the β3-adrenoceptor, in aging rat bladder function in vitro and to test the therapeutic effect of SQW on LUTS in an aging rat model based on the β3-adrenoceptor. Briefly, the bladder detrusor muscles of young (age, 3 months) and aging (age, 15 months) female rats were separated. A β-AR non-selective agonist, isoprenaline (ISO), subtype β3-AR agonist (BRL37344A) and β3-AR antagonist (SR59230A) were used to define the tension change of detrusor muscles between young and aging rats in vitro. For blank controls, 12 young rats were marked, and 48 aging female rats were randomly divided into four groups as follows: Model, SQW high, SQW middle and SQW low. Following oral administration of SQW for 6 weeks in aging rats, urodynamic and bladder detrusor tests were used to evaluate the therapeutic effect of SQW. The expression of β3-AR mRNA was investigated using reverse transcription-quantitative polymerase chain reaction. Using ISO and BRL37344A in vitro, maximum relaxation (Emax), intrinsic activity (IA), and log (50% effective concentration) (PD2) were significantly decreased in aging rats compared with that in young rats (P<0.05). Significant changes were also observed in the β3-AR antagonist experiment, which blocked ISO-induced relaxation, with significant decreases observed in Emax, IA and PD2, and a significant increase observed in PA2 for the aging rats compared with the young controls (P<0.05). SQW was demonstrated to enhance bladder control, storage and contraction ability. Furthermore, SQW was able to increase the sensitivity and expression of β3-AR in an aging rat. In conclusion, the decrease in β3-AR sensitivity in aging rats and the expression resulted in bladder detrusor dysfunction. In addition, the therapeutic effect of SQW against LUTS relies on the former's effect on the urethral sphincter, bladder detrusor and β3-AR.

194 - 9-Phenanthrol modifies rat bladder function independent of TRPM4

194 - 9-Phenanthrol modifies rat bladder function independent of TRPM4

Effects of pulsed-radiofrequency neuromodulation on the rat with overactive bladder.

To quantify the effects of pulsed radiofrequency (PRF) electrical stimulations of the pudendal and pelvic nerves on the bladder function of rats with detrusor overactivity. All rats were pretreated with a continuous transvesical infusion of 0.5% acetic acid (AA) for inducing detrusor overactivity. Intravesical pressure was recorded using cysometrography (CMG) during the continuous transvesical infusion to examine the effects of PRF electrical stimulation of the pudendal and pelvic nerves individually. In addition, the activity of caspase-3, an apoptosis marker, in the pelvic nerve was examined to evaluate the impact of PRF on nerve injury. According to the first CMG recording, AA treatment significantly reduced bladder capacity (BC) and intercontraction interval (ICI) to 65% and 66% of the corresponding control values, respectively. Subsequently, PRF electrical stimulation of the pelvic nerve inhibited AA-induced detrusor overactivity and significantly increased BC to approximately 102-110% and ICI to 79-92%; these effects persisted for at least 4 h. Furthermore, PRF did not cause significant neural damage to the target stimulated nerves, as demonstrated by caspase-3 activity. PRF electrical stimulation of pelvic nerves exerted a long-lasting effect of suppressing AA-induced detrusor overactivity. This modality can be used as an alternative approach for improving bladder continence in patients with overactive bladder syndrome.

Effects of Duloxetine on Urethral Continence Reflex and Bladder Activity in Rats with Cerebral Infarction

We investigated the effect of duloxetine, a norepinephrine and serotonin reuptake inhibitor, on the sneeze induced continence reflex and on bladder function in rats with cerebral infarction. Using urethane anesthesia the effect of duloxetine (1 mg/kg intravenously) on the amplitude of urethral responses during sneezing as well as urethral baseline pressure at the mid urethra was evaluated in normal female adult rats and cerebral infarction rats. Tilt leak point pressure was also measured. In normal and cerebral infarction rats continuous cystometry was evaluated before and after duloxetine injection. In cerebral infarction rats urethral baseline pressure was 43% lower than in normal rats but the amplitude of urethral responses during sneezing did not differ in the 2 groups. Duloxetine increased the amplitude of urethral responses during sneezing and urethral baseline pressure by 31% and 21%, respectively, in normal rats but did not affect either in cerebral infarction rats. Also, in cerebral infarction rats leak point pressure was 29% lower compared with normal rats. Duloxetine increased leak point pressure in normal rats but not in cerebral infarction rats. Cerebral infarction reduced intercontraction intervals without affecting the amplitude of bladder contractions compared with normal rats. Duloxetine prolonged intercontraction intervals in cerebral infarction rats but not in normal rats. These results suggest that cerebral infarction induces not only bladder overactivity but also stress urinary incontinence, which may account for mixed incontinence in patients with cerebral infarction. After cerebral infarction duloxetine reduced bladder overactivity but failed to enhance active urethral closure mechanisms during sneezing, suggesting that disorganization of the brain network after cerebral infarction might influence the effect of duloxetine on lower urinary tract function.

Optogenetics applications for treating spinal cord injury.

Cases of spinal cord injury (SCI) are increasing all over the world; and in USA alone, there are 273,000 patients, which not only leads to morbidity and mortality but also results in a great economic burden. Many approaches are being used at the pre-clinical and clinical level to treat SCI including therapeutic agents, surgical decompression, stem cell therapy etc. Recently, a new approach called optogenetics has emerged in which light sensitive proteins are used to switch neurons on and off, and this approach has great potential to be used as therapy due to its specificity and rapid response in milliseconds. Few animal studies have been performed so far in which the respiratory and bladder function of rats was restored through the use of optogenetics. On the basis of promising results obtained, in the future, this approach can prove to be a valuable tool to treat patients with SCI.

Influence of urethane-anesthesia on the effect of resiniferatoxin treatment on bladder function in rats with spinal cord injury

We investigated the effect of resiniferatoxin (RTX)-treatment on cystometric parameters in the spinal cord injury (SCI) rats in both conscious and urethane-anesthetized conditions and evaluated the influence of urethane-anesthesia on the effect of RTX on lower urinary tract (LUT) function in SCI rats. Female Sprague-Dawley rats were used. SCI was created by transection of the T8-T9 spinal cord. Four weeks after the transection, the animals were placed in a restraint cage for the first cystometric measurements in a conscious state. Secondary cystometric measurements were performed in a conscious condition following the 1 day after RTX-(0.3 mg/kg) or vehicle-subcutaneous injection. Then the animals were injected with urethane (1.5 g/kg, subcutaneously), and cystometric measurements were repeated four times every 1 hr-interval. After the RTX-treatment in a conscious condition, urinary retention was observed in three out of five animals. In addition, the number of non-voiding contractions (NVCs) significantly decreased although their amplitude did not change significantly. After the urethane-injection, all of the animals treated with RTX developed urinary retention. The amplitude of NVCs significantly decreased, whereas the number of NVCs did not change significantly in the RTX-treated group. No cystometric parameters significantly changed after either vehicle- or urethane-injection in the vehicle-treated group. The present results indicate that the suppressive effects of RTX on NVCs as well as voiding contractions in SCI rats can be enhanced by urethane-anesthesia. Such suppressive effect of urethane-anesthesia itself should be taken into consideration when we evaluate a drug-effect on LUT function in rats with SCI.

A Microchannel Neuroprosthesis for Bladder Control After Spinal Cord Injury in Rat

A severe complication of spinal cord injury is loss of bladder function (neurogenic bladder), which is characterized by loss of bladder sensation and voluntary control of micturition (urination), and spontaneous hyperreflexive voiding against a closed sphincter (detrusor-sphincter dyssynergia). A sacral anterior root stimulator at low frequency can drive volitional bladder voiding, but surgical rhizotomy of the lumbosacral dorsal roots is needed to prevent spontaneous voiding and dyssynergia. However, rhizotomy is irreversible and eliminates sexual function, and the stimulator gives no information on bladder fullness. We designed a closed-loop neuroprosthetic interface that measures bladder fullness and prevents spontaneous voiding episodes without the need for dorsal rhizotomy in a rat model. To obtain bladder sensory information, we implanted teased dorsal roots (rootlets) within the rat vertebral column into microchannel electrodes, which provided signal amplification and noise suppression. As long as they were attached to the spinal cord, these rootlets survived for up to 3 months and contained axons and blood vessels. Electrophysiological recordings showed that half of the rootlets propagated action potentials, with firing frequency correlated to bladder fullness. When the bladder became full enough to initiate spontaneous voiding, high-frequency/amplitude sensory activity was detected. Voiding was abolished using a high-frequency depolarizing block to the ventral roots. A ventral root stimulator initiated bladder emptying at low frequency and prevented unwanted contraction at high frequency. These data suggest that sensory information from the dorsal root together with a ventral root stimulator could form the basis for a closed-loop bladder neuroprosthetic.

Effects of Vitamin D Analog on Bladder Function and Sensory Signaling in Animal Models of Cystitis

To measure the effects of nonhypercalcemic vitamin D receptor agonist elocalcitol on bladder function in rats with cyclophosphamide-induced cystitis and on bladder function and sensory nerve activity in a mouse with acetic acid-evoked bladder irritation. Female Wistar rats and male Balb/C mice were gavaged once daily with elocalcitol diluted in miglyol 812 (treatment group) or miglyol alone (control group). On experimental day 12, polyethylene tubing was implanted into the urinary bladder in all the animals. In the mice, a bipolar electrode was positioned under a single postganglionic bladder nerve. At 48 hours after surgery, bladder function was measured in awake, freely moving rats during bladder filling with 0.9% NaCl and both bladder function and sensory nerve activity was measured in awake, restrained mice during continuous intravesical infusion of 0.9% NaCl followed by 0.25% acetic acid. In rats, the treatment group showed a significant increase in bladder capacity and decrease in number of nonvoiding bladder contractions. In mice, the filling pressure during saline infusion was similar in both groups; however, during acetic acid infusion, the average filling pressure was significantly increased (47%) in the control group but not in the elocalcitol treatment group. The firing rate at filling pressure for the treatment group was 3.6-fold and 2.7-fold lower than that in the control group during the saline and acetic acid infusion, respectively. Oral treatment with elocalcitol suppressed signs of detrusor overactivity in both animal models and exerted strong suppressive effect on urinary bladder sensory signaling during filling in mice.

Effect of different durations of overdistention on rat bladder function and morphology

We investigated the contribution of the duration of overdistention (DOD) to rat bladder function and morphology and explored its possible molecular mechanisms. Bladder overdistention was induced in male Sprague-Dawley rats (200-250 g) by an infusion of saline. Forty rats were divided into 5 groups submitted to different DOD, i.e., 1, 2, 4, and 8 h, and control. Bladder function was evaluated by cystometry. Morphological changes were observed by light and transmission electron microscopy. Compared to control (44.567 ± 3.472 cmH2O), the maximum detrusor pressure of groups with 2-, 4- and 8-h DOD decreased significantly (means ± SEM): 32.774 ± 3.726, 31.321 ± 2.847, and 29.238 ± 3.724 cmH2O. With the increase of DOD, inflammatory infiltration and impairment of ultrastructure were more obvious in bladder tissue. Compared to control (1.90 ± 0.77), the apoptotic indexes of groups with 1-, 2-, 4-, and 8-h DOD increased significantly (6.47 ± 2.10, 10.66 ± 1.97, 13.91 ± 2.69, and 18.33 ± 3.28%). Compared to control (0.147 ± 0.031/0.234 ± 0.038 caspase 3/β-actin and Bax/Bcl-2 ratios), both caspase 3/β-actin and Bax/Bcl-2 ratios of 1-, 2-, 4-, and 8-h DOD increased significantly (0.292 ± 0.037/0.508 ± 0.174, 0.723 ± 0.173/1.745 ± 0.471, 1.104 ± 0.245/4.000 ± 1.048, and 1.345 ± 0.409/8.398 ± 3.332). DOD plays an important role in impairment of vesical function and structure. With DOD, pro-apoptotic factors increase and anti-apoptotic factors decrease, possibly contributing to the functional deterioration and morphological changes of the bladder.

Effects of ritobegron (KUC-7483), a novel β&lt;sub&gt;3&lt;/sub&gt;-adrenoceptor agonist, on both rat bladder function following partial bladder outlet obstruction and on rat salivary secretion: a comparison with the effects of tolterodine

The objective of this study was to investigate the effects of the β3-adrenoceptor (AR) agonist ritobegron on rat bladder function following partial bladder outlet obstruction and on rat salivary secretion. In addition, the effects of ritobegron were compared with those of the anti-muscarinic agent tolterodine. After a 6-week partial bladder outlet obstruction (BOO), drug effects on bladder functions were evaluated using cystometrography. Effects on carbachol (CCh)-induced salivary secretion were evaluated in urethane-anesthetized rats. Ritobegron significantly decreased the frequency of non-voiding contractions (NVC), while both ritobegron and tolterodine each significantly decreased the amplitude of NVC. Ritobegron had no effect on either the micturition pressure (MP) or the residual volume (RV). In contrast, tolterodine dose-dependently decreased MP and increased RV. Ritobegron had no effect on CCh-induced salivary secretion, whereas tolterodine dose-dependently decreased it. Ritobegron decreased both the frequency and amplitude of NVC, which is similar to its effect on the contractions associated with detrusor overactivity (DO) in patients with an overactive bladder (OAB), without affecting MP, RV, or CCh-induced salivary secretion. Although tolterodine reduced the amplitude of NVC, it also markedly increased RV and significantly inhibited CCh-induced salivary secretion. These results suggest that use of ritobegron, a β3-AR agonist, is unlikely to lead to the residual urine and dry mouth symptoms that are associated with anti-muscarinic drugs, and that ritobegron may hold promise as a safe and effective agent for OAB treatment.

Kv7 Positive Modulators Reduce Detrusor Overactivity and Increase Bladder Capacity in Rats

The effects of the Kv 7 channel modulators retigabine (opener) and XE991 (blocker) on rat bladder function were investigated ex vivo and in vivo to assess the potential of Kv 7 openers for the treatment of overactive bladder. In organ bath studies, capsaicin-stimulated rat urinary bladder rings were exposed to retigabine and XE991 and the effect on tension and amplitude was evaluated. In anaesthetized rats, retigabine (0.01-1 mg/kg, i.v.) effects on bladder function, in which overactivity was induced by continuous infusion of 0.5% acetic acid, were assessed. The effect of retigabine (10 mg/kg, p.o.) on cystometric parameters was also measured in conscious rats with capsaicin-induced irritated bladders. Localization of Kv 7 subunits within bladder tissue was analysed by RT-qPCR and western blotting. In organ bath studies, retigabine robustly reduced capsaicin-induced contractility of bladder rings and this effect was blocked by XE991 confirming the specificity of action via Kv 7 channels. In anaesthetized rats with acetic acid-irritated bladders, retigabine markedly increased bladder capacity with no concomitant reduction in blood pressure. Retigabine also reduced bladder pressure and delayed voiding in conscious rats with capsaicin-irritated bladders. Kv 7.1, Kv 7.4 and Kv 7.5 subunit mRNA transcripts were detected in rat bladder. Western blot analysis confirmed that Kv 7.4 subunit protein was expressed in rat bladder. These results suggest that retigabine and other Kv 7 channel positive modulators may have beneficial effects on bladder overactivity partly via activation of Kv 7 channels expressed in bladder tissue.

Distribution of Convergent Afferents Innervating Bladder and Prostate at Dorsal Root Ganglia in Rats

To investigate the distribution of dichotomizing afferents supplying both the prostate and urinary bladder, and to discern the effects of noxious stimulation of the prostate on urinary bladder function in rats. Dual retrograde fluorescence labeling was used to investigate the neurogenic aspect of urinary bladder function. The dual distribution of dorsal root ganglia (DRG) cells was determined by propidium iodide (PI) and propidium bisbenzimide (Bb) staining into the prostate and bladder. To examine mechanical sensitivity of the bladder, conscious filling cystometry was performed before and after completion of Freund adjuvant injection into the prostate. Double-labeled positive cells were found in the lumbosacral DRG, predominantly in L1-L2 and L6-S1, with distribution varyinig from 7.5% to 14%. Most of the double-labeled cells were classified as small and medium in size. Prostatic irritation had no effect on the number of labeled cells. With the use of cystometry, prostatic irritation was found to shorten mean micturition interval (P <.05), decrease mean volume threshold inducing micturition, and increase baseline pressure and threshold pressure (P <.05), but to lower peak micturition pressure compared with that in controls (P <.01). These findings suggest that bladder-prostate convergent DRG neurons may play a role in bladder-prostate cross-sensitization after prostatitis. This study also provided neuronal anatomical evidence for voiding dysfunction associated with chronic prostatitis/chronic pelvic pain syndrome.

Olfactory Mucosal Transplantation After Spinal Cord Injury Improves Voiding Efficiency by Suppressing Detrusor-Sphincter Dyssynergia in Rats

Several recent studies showed that olfactory mucosal transplantation after spinal cord injury promotes extensive regeneration of the injured spinal cord. We examined the efficacy of olfactory mucosal transplantation for bladder dysfunction after spinal cord injury in rats. In adult female rats the Th9-10 spinal cord was completely transected, followed by olfactory mucosal transplantation or gelatin sponge filling as the control. Each group was examined by cystometrogram and external urethral sphincter electromyogram. Calcitonin gene-related peptide and growth associated protein 43 double positive expression in the L6/S1 dorsal horn was evaluated by immunohistochemistry. Transplant sites were examined by immunohistochemistry with antibodies against neurofilament M and neuronal class III beta-tubulin. On cystometrogram voiding efficiency was significantly higher in the transplantation group than in controls. On external urethral sphincter electromyogram with simultaneous cystometrogram the transplantation group showed a larger ratio of interburst silent periods to burst activity duration and a greater number of high frequency oscillations. In the transplantation group calcitonin gene-related peptide and growth associated protein 43 double positive expression in the L6/S1 dorsal horn was less dense than in controls. The transplantation group showed strong neurofilament M and neuronal class III beta-tubulin expression at the transplant site. Olfactory mucosal transplantation after spinal cord injury weakened external urethral sphincter excessive bursting and increased the urethral opening to improve voiding efficiency. Olfactory mucosal transplantation may modify emergence of the spinal micturition reflex after spinal cord injury. Transplantation resulted in new axons growing at the transplant site, implying the possible existence of interneuron bridging across the injured spinal cord.

Effects of Cannabinor, a Novel Selective Cannabinoid 2 Receptor Agonist, on Bladder Function in Normal Rats

BackgroundCannabinoid (CB) receptors may be involved in the control of bladder function; the role of CB receptor subtypes in micturition has not been established. ObjectivesOur aim was to evaluate the effects of cannabinor, a novel CB2 receptor agonist, on rat bladder function. Design, setting, and participantsSprague Dawley rats were used. Distribution of CB2 receptors in sensory and cholinergic nerves of the detrusor was studied. Selectivity of cannabinor for human and rat CB receptors was evaluated. Effects of cannabinor on rat detrusor and micturition were investigated. MeasurementsImmunohistochemistry, radioligand binding, tritium outflow assays, organ bath studies of isolated bladder tissue, and cystometry in awake rats were used. Results and limitationsCB2 receptor immunoreactivity was expressed in the urothelium and in sensory and cholinergic bladder nerves. Cannabinor exhibited similar binding at human and rat CB2 receptors and a 321-fold functional selectivity for the CB2 receptor versus the CB1 receptor. Cannabinor had no effect on isolated detrusor muscle function. In vivo, cannabinor 3.0mg/kg increased micturition intervals and volumes by 52% (p<0.05) and 96% (p<0.01), respectively, and increased threshold and flow pressures by 73% (p<0.01) and 49% (p<0.001), respectively. Cannabinor 0.3 or 1.0mg/kg or vehicle did not affect urodynamic parameters. ConclusionsConsidering that CB2 receptors are localized on sensory nerves and on the urothelium and that cannabinor had effects on “afferent” urodynamic parameters, peripheral CB2 receptors may be involved in sensory functions of rat micturition. Effects of cannabinor on cholinergic nerve activity in normal bladder tissue appear to be limited.