A neurologic basis for the overactive bladder

Fesoterodine

black triangle Fesoterodine is a muscarinic receptor antagonist that is rapidly and extensively converted to the active and more potent metabolite 5-hydroxymethyltolterodine. The drug is approved for once-daily oral administration in patients with overactive bladder syndrome (OAB). black triangle In two large, 12-week, randomized, double-blind, multicentre, phase III trials, oral fesoterodine 4 or 8 mg once daily improved the symptoms of OAB (frequency of micturition, urgency and urge incontinence) significantly more than placebo. black triangle Furthermore, significantly more patients receiving fesoterodine 4 or 8 mg once daily had a positive response to therapy than those receiving placebo, as determined by a treatment questionnaire. black triangle Health-related quality of life was improved to a significantly greater extent in patients with OAB who received fesoterodine 4 or 8 mg once daily than in those who received placebo in a post hoc analysis of pooled data from the phase III trials. black triangle Fesoterodine 4 or 8 mg once daily was generally well tolerated in patients with OAB; the most frequent adverse event was dry mouth, which was generally mild to moderate in severity.

Adaptation of the length-active tension relationship in rabbit detrusor

Studies have shown that the length-tension (L-T) relationships in airway and vascular smooth muscles are dynamic and can adapt to length changes over a period of time. Our prior studies have shown that the passive L-T relationship in rabbit detrusor smooth muscle (DSM) is also dynamic and that DSM exhibits adjustable passive stiffness (APS) characterized by a passive L-T curve that can shift along the length axis as a function of strain history and activation history. The present study demonstrates that the active L-T curve for DSM is also dynamic and that the peak active tension produced at a particular muscle length is a function of both strain and activation history. More specifically, this study reveals that the active L-T relationship, or curve, does not have a unique peak tension value with a single ascending and descending limb, but instead reveals that multiple ascending and descending limbs can be exhibited in the same DSM strip. This study also demonstrates that for DSM strips not stretched far enough to reveal a descending limb, the peak active tension produced by a maximal KCl-induced contraction at a short, passively slack muscle length of 3 mm was reduced by 58.6 +/- 4.1% (n = 15) following stretches to and contractions at threefold the original muscle length, 9 mm. Moreover, five subsequent contractions at the short muscle length displayed increasingly greater tension; active tension produced by the sixth contraction was 91.5 +/- 9.1% of that produced by the prestretch contraction at that length. Together, these findings indicate for the first time that DSM exhibits length adaptation, similar to vascular and airway smooth muscles. In addition, our findings demonstrate that preconditioning, APS and adaptation of the active L-T curve can each impact the maximum total tension observed at a particular DSM length.

A refocus on the bladder as the originator of storage lower urinary tract symptoms: a systematic review of the latest literature

CONTEXT

The focus of clinical understanding and management of male storage lower urinary tract symptoms (LUTS) has shifted from the prostate to the bladder. This is mirrored by an increasing body of experimental evidence suggesting that the bladder is the central organ in the pathogenesis of LUTS.

OBJECTIVE

A systematic review of the literature available on pathophysiologic aspects of storage LUTS.

EVIDENCE ACQUISITION

Medline was searched for the period ending December 2008 for studies on human and animal tissue exploring possible functional and structural alterations underlying bladder dysfunction. Further studies were chosen on the basis of manual searches of reference lists and review papers.

EVIDENCE SYNTHESIS

Numerous recent publications on LUTS pathophysiology were identified. They were grouped into studies exploring abnormalities on urothelial/suburothelial, muscular, or central levels.

CONCLUSIONS

Studies revealed both structural and functional alterations in bladders from patients with LUTS symptoms or animals with experimentally induced bladder dysfunction. In particular, the urothelium and the suburothelial space, containing afferent nerve fibres and interstitial cells, have been found to form a functional unit that is essential in the process of bladder function. Various imbalances within this suburothelial complex have been identified as significant contributors to the generation of storage LUTS, along with potential abnormalities of central function.

Long-term implantation of deep brain stimulation electrodes in the pontine micturition centre of the Göttingen minipig

AIM

To implant deep brain stimulation (DBS) electrodes in the porcine pontine micturition centre (PMC) in order to establish a large animal model of PMC-DBS.

METHOD

Brain stems from four Göttingen minipigs were sectioned coronally into 40-mum-thick histological sections and stained with Nissl, auto-metallographic myelin stain, tyrosine hydroxylase and corticotrophin-releasing factor immunohistochemistry in order to identify the porcine PMC. DBS electrodes were then stereotaxically implanted on the right side into the PMC in four Göttingen minipigs, and the bladder response to electrical stimulation was evaluated by subsequent cystometry performed immediately after the operation and several weeks later.

FINDINGS

A paired CRF-dense area homologous to the PMC in other species was encountered in the rostral pontine tegmentum medial to the locus coeruleus and ventral to the floor of the fourth ventricle. Electrical stimulation of the CRF-dense area resulted in an increased detrusor pressure followed by visible voiding in some instances. The pigs were allowed to survive between 14 and 55 days, and electrical stimulation resulting in an increased detrusor pressure was performed on more than one occasion without affecting consciousness or general thriving. None of the pigs developed postoperative infections or died prematurely.

CONCLUSIONS

DBS electrodes can be implanted for several weeks in the identified CRF-dense area resulting in a useful large animal model for basic research on micturition and the future clinical use of this treatment modality in neurogenic supra-pontine voiding disorders.

Bladder dysfunction in multiple sclerosis

Multiple sclerosis (MS) is a relatively common disease of young adults. Patients with MS can have a wide range of symptoms and may develop significant disability. The cause of MS is unknown, but immunological mechanisms are important. In MS, the pathological features include prominent demyelination and inflammation, but there is also evidence of neurodegeneration. Bladder symptoms are common in MS. The bladder is under neural control, and bladder disturbance is usually attributed to demyelination or loss of axons from the neural pathways, particularly those in the spinal cord, that control the bladder. However, as with other symptoms in MS, the presence of bladder disturbance does not always correlate well with MRI lesions. We speculate that other possible causes of bladder dysfunction in MS might include the effects of circulating toxic factors. Urgency of micturition is prominent in MS, and better understanding of the receptors involved in bladder sensation suggests possible treatment strategies through inhibiting these receptors.

Basic fibroblast growth factor causes urinary bladder overactivity through gap junction generation in the smooth muscle

Overactive bladder is a highly prevalent clinical condition that is often caused by bladder outlet obstruction (BOO). Increased coupling of bladder smooth muscle cells (BSMC) via gap junctions has been hypothesized as a mechanism for myogenic bladder overactivity in BOO, although little is known about the regulatory system underlying such changes. Here, we report the involvement of basic fibroblast growth factor (bFGF) and connexin 43, a bladder gap junction protein, in bladder overactivity. BOO created by urethral constriction in rats resulted in elevated bFGF and connexin 43 levels in the bladder urothelium and muscle layer, respectively, and muscle strips from these bladders were more sensitive than those from sham-operated controls to a cholinergic agonist. In vitro bFGF treatment increased connexin 43 expression in cultured rat BSMC via the ERK 1/2 pathway. This finding was supported by another in vivo model, where bFGF released from gelatin hydrogels fixed on rat bladder walls caused connexin 43 upregulation and gap junction formation in the muscle layer. Bladder muscle strips in this model showed increased sensitivity to a cholinergic agonist that was blocked by inhibition of gap junction function with alpha-glycyrrhetinic acid. Cystometric analyses of this model showed typical features of detrusor overactivity such as significantly increased micturition frequency and decreased bladder capacity. These findings suggest that bFGF from the urothelium could induce bladder hypersensitivity to acetylcholine via gap junction generation in the smooth muscle, thereby contributing to the myogenic overactivity of obstructed bladders.

Gosha-jinki-gan reduces transmitter proteins and sensory receptors associated with C fiber activation induced by acetic acid in rat urinary bladder

AIM

We determined if Gosha-jinki-gan, a traditional Chinese herbal mixture, reduced the presence of the tachykinins neurokinin A, neurokinin B, and substance P, as well as the transient receptor potential vanilloid 1 (TRPV1) and P2X3 purine receptors that are functionally associated with C fibers in the urinary bladder.

METHODS

Thirty-six female rats were fed with either a standard diet or one supplemented with 1.08% Gosha-jinki-gan. After 4 weeks, the urinary bladders were instilled with either saline or 0.1% acetic acid. After 30 min, the bladders were removed and expression of the tachykinins and the TRPV1 and P2X3 receptors was determined by immunohistochemistry and mRNA expression.

RESULTS

In rats fed with the standard diet, the tachykinins and the TRPV1 and P2X3 receptors expressed nearby or within urothelium of the acetic acid-treated rats increased compared with the saline-instilled rats. In rats pretreated with Gosha-jinki-gan, the tachykinins and the TRPV1 and P2X3 receptors in the acetic acid-treated rats also increased compared with the saline-instilled rats. However, with the instillation of acetic acid, the tachykinins and the TRPV1 and P2X3 receptors of Gosha-jinki-gan pretreated rats decreased compared with standard diet fed rats. The mRNA expression levels of neurokinin A, substance P, and the TRPV1 receptor in acetic acid-treated Gosha-jinki-gan pretreated rats were lower than that in acetic acid-treated standard diet fed rats. Gosha-jinki-gan did not destroy nerve fibers within the bladders.

CONCLUSIONS

Gosha-jinki-gan partially reduced the tachykinins and TRPV1 and P2X3 purine receptors without destroying the nerve fibers.

In vivo and in vitro pharmacological characterization of SVT-40776, a novel M3 muscarinic receptor antagonist, for the treatment of overactive bladder

BACKGROUND AND PURPOSE

Highly selective M(3) muscarinic receptor antagonists may represent a better treatment for overactive bladder syndrome, diminishing side effects. Cardiac side effects of non-selective antimuscarinics have been associated with activity at M(2) receptors as these receptors are mainly responsible for muscarinic receptor-dependent bradycardia. We have investigated a novel antimuscarinic, SVT-40776, highly selective for M(3) over M(2) receptors (Ki = 0.19 nmol.L(-1) for M(3) receptor affinity). This study reports the functional activity of SVT-40776 in the bladder, relative to its activity in atria.

EXPERIMENTAL APPROACH

In vitro and ex vivo (oral dosing) inhibition of mouse detrusor and atrial contractile responses to carbachol were used to study the functional activity of SVT-40776. The in vivo efficacy of SVT-40776 was characterized by suppression of isovolumetric spontaneous bladder contractions in anaesthetized guinea pigs after intravenous administration.

KEY RESULTS

SVT-40776 was the most potent in inhibiting carbachol-induced bladder contractions of the anti-cholinergic agents tested, without affecting atrial contractions over the same range of concentrations. SVT-40776 exhibited the highest urinary versus cardiac selectivity (199-fold). In the guinea pig in vivo model, SVT-40776 inhibited 25% of spontaneous bladder contractions at a very low dose (6.97 microg.kg(-1) i.v), without affecting arterial blood pressure.

CONCLUSIONS AND IMPLICATIONS

SVT-40776 is a potent inhibitor of M(3) receptor-related detrusor contractile activity. The absence of effects on isolated atria preparations represents an interesting characteristic and suggests that SVT-40776 may lack unwanted cardiac effects; a feature especially relevant in a compound intended to treat mainly elderly patients.

Spontaneous contractions evoke afferent nerve firing in mouse bladders with detrusor overactivity

PURPOSE

Afferent nerve firing has been linked to spontaneous bladder contractions in a number of lower urinary tract pathologies and it may lead to urgency and incontinence. Using optical mapping, single unit recording and tension measurements we investigated the correlation between afferent nerve firing and spontaneous bladder contractions in spinal cord transected mice.

MATERIALS AND METHODS

Bladder-nerve preparations (bladder sheets and the associated L6-S2 pelvic nerves) were dissected from normal and spinal cord transected mice showing overactivity on cystometry and opened along the ventral aspect from base to dome. Bladder sheets were mounted horizontally in a temperature regulated chamber to simultaneously record Ca(2+) transients across the mucosal surface, single unit afferent nerve firing and whole bladder tension.

RESULTS

Single unit afferent fibers were identified by probing their receptive fields. Fibers showed a graded response to von Frey stimulation and a frequency of afferent firing that increased as a function of the degree of stretch. Optical maps of Ca(2+) transients in control bladders demonstrated multiple initiation sites that resulted in high frequency, low amplitude spontaneous contractions. Alternatively in maps of the bladders of spinal cord transected mice Ca(2+) transients arose from 1 or 2 focal sites, resulting in low frequency, high amplitude contractions and concomitant afferent firing.

CONCLUSIONS

Large amplitude, spontaneous bladder contractions evoke afferent nerve activity, which may contribute to incontinence.

Emerging drugs for treatment of overactive bladder and detrusor overactivity

BACKGROUND

Overactive bladder (OAB) signifies the presence of urinary urgency and can have major effects on quality of life and social functioning. Standard antimuscarinic drugs have good initial response rates but substantial adverse effects and long-term compliance problems.

OBJECTIVES

To review the complexities of the mechanisms underlying OAB and the current drugs available for treating its symptoms.

METHODS

The literature was reviewed to define current therapies and drugs in clinical trials. Articles were identified by means of a computerised PubMed and Cochrane Library search (using the following keywords: overactive bladder, detrusor overactivity, urgency and bladder), supported by a search of the PharmaProjects database.

CONCLUSIONS

New drug classes, such as beta-3 adrenergic agonists, may work by reducing contractility or excitability of bladder muscle. Moderation of afferent activity may allow improved OAB symptoms, with lower risk of affecting voiding function. Agents acting on the CNS could influence OAB favourably, but target selection and adverse effects are an issue. The recognition of the functional contribution of the urothelium and the diversity of nerve transmitters has sparked interest in both peripheral and central modulation of OAB pathophysiology.

Bladder control, urgency, and urge incontinence: evidence from functional brain imaging

AIM

To review brain imaging studies of bladder control in subjects with normal control and urge incontinence; to define a simple model of supraspinal bladder control; and to propose a neural correlate of urgency and possible origins of urge incontinence.

METHODS

Review of published reports of brain imaging relevant to urine storage, and secondary analyses of our own recent observations.

RESULTS

In a simple model of normal urine storage, bladder and urethral afferents received in the periaqueductal gray (PAG) are mapped in the insula, forming the basis of sensation; the anterior cingulate gyrus (ACG) provides monitoring and control; the prefrontal cortex makes voiding decisions. The net result, as the bladder fills, is inhibition of the pontine micturition center (PMC) and of voiding, together with gradual increase in insular response, corresponding to increasing desire to void. In urge-incontinent subjects, brain responses differ. At large bladder volumes and strong sensation, but without detrusor overactivity (DO), most cortical responses become exaggerated, especially in ACG. This may be both a learned reaction to previous incontinence episodes and the neural correlate of urgency. The neural signature of DO itself seems to be prefrontal deactivation. Possible causes of urge incontinence include dysfunction of prefrontal cortex or limbic system, suggested by weak responses and/or deactivation, as well as abnormal afferent signals or re-emergence of infantile reflexes.

CONCLUSIONS

Bladder control depends on an extensive network of brain regions. Dysfunction in various parts may contribute to urge incontinence, suggesting that there are different phenotypes requiring different treatments.

Altered distribution of interstitial cells in the guinea pig bladder following bladder outlet obstruction

AIMS

We investigated the effects of bladder outlet obstruction (BOO) on the distribution of interstitial cells (ICs) in the guinea-pig bladder.

METHODS

Bladder overactivity of BOO animals was validated with urodynamic studies. Immunohistochemical analyses for Kit and vimentin as markers for ICs were performed on both BOO and control bladders. Morphological and functional properties of detrusor smooth muscle (DSM) were examined with alpha-smooth muscle actin staining and intracellular recording, respectively. Electron microscopy was also carried out to characterize ultrastructural morphology of ICs.

RESULTS

Two weeks after surgery, BOO animals showed an increased voiding frequency and a reduced voiding volume. Filling cystometry demonstrated a frequent incidence of non-voiding contractions, a reduced interval between voiding contractions and an increased voiding pressure in BOO bladders. In BOO bladders, the thickness of suburothelial and subserosal connective tissue layers was increased, whilst that of detrusor smooth muscle (DSM) layer was less affected. Population of Kit or vimentin immunoreactive ICs was increased in subserosal layers, and their distribution was altered in suburotherial layer in BOO bladders. Neither alpha-actin immunoreactivity nor spontaneous electrical activity of DSM was altered in BOO bladders. ICs were characterized by their numerous mitochondria and caveolae, and had a close contact with each other and with neighboring DSM or nerves.

CONCLUSIONS

These results demonstrated the increased population of ICs in the BOO guinea-pig model for the first time, and suggest that the altered distribution of ICs may contribute to the pathophysiology of bladder overactivity.

The effects of long-term spinal cord injury on mechanical properties of the rat urinary bladder

We have demonstrated that bladder wall tissue in spinal cord injury (SCI) rats at 10 days post-injury is more compliant and accompanied by changes in material class from orthotropic to isotropic as compared to normal tissue. The present study examined the long-term effects (3-, 6-, and 10-weeks) post-SCI on the mechanical properties of bladder wall tissues, along with quantitative changes in smooth muscle orientation and collagen and elastin content. Bladder wall compliance (defined as det(F) - 1 under an equi-biaxial stress state of 100 kPa, where F is the deformation gradient tensor) was found to be significantly greater at 3- and 6-weeks (0.873 +/- 0.092 and 0.864 +/- 0.112, respectively) when compared to the normal bladders (0.260 +/- 0.028), but at 10 weeks the compliance reduced (0.389 +/- 0.061) to near that of normal bladders. This trend in mechanical compliance closely paralleled the collagen/elastin ratio. Moreover, changes in material class, assessed using a graphical technique, correlated closely with quantitative changes in smooth muscle fiber orientation. The results of the present study provide the first evidence that, while similarities exist between acute and chronic responses of the urinary bladder wall tissue to SCI, the overall alterations are distinct, result in profound and complex time dependent changes in bladder wall structure, and will lay the basis for simulations of the bladder wall disease process.

The loss and progressive recovery of voiding after spinal cord interruption in rats is associated with simultaneous changes in autonomous contractile bladder activity

BACKGROUND

Autonomous contractile activity (ACA) is a well-known phenomenon in isolated bladders from different species and seems to be important in the physiology of both normal and dysfunctional voiding.

OBJECTIVE

To determine whether ACA is changed in bladders from paraplegic rats at different periods post-spinal cord injury (post-SCI).

DESIGN, SETTING, AND PARTICIPANTS

ACA was studied in bladders (at least six per group) from normal and paraplegic female Wister rats at different times post-SCI (2 h, 24 h, 1 wk, and 3 wk). A group of normal rats was used as a control group. For measurements bladders were incubated in organ baths under standardised conditions.

MEASUREMENTS

ACA was measured as pressure change, which was defined as either a transient change or a spiked change according to its characteristics. The effects of intravesical volume load and muscarinic agonists were studied.

RESULTS AND LIMITATIONS

Following spinal cord injury (SCI) a clear evolution in ACA was observed. In bladders from SCI rats in the acute areflexive voiding phase (1 wk post-SCI), we observed decreased ACA associated with a highly increased compliance and a changed response to muscarinic agonists. ACA in bladders from SCI rats with renewed voiding reflexes (3 wk post-SCI) was increased, together with a moderately increased compliance and a (moderately) changed response to muscarinic agonists.

CONCLUSIONS

From these observations it is apparent that SCI leads to alterations in the behaviour and muscarinic response of ACA in the isolated bladder. These changes in ACA may play an important role in the pathophysiology of overactive bladder disease (OAB), and interacting with changed ACA might be promising in the search for newer treatments for OAB.

Urotheliogenic modulation of intrinsic activity in spinal cord-transected rat bladders: role of mucosal muscarinic receptors

We examined the modulation of intrinsic (i.e., spontaneous) detrusor contractions by the urothelium and the lamina propria through optical mapping approaches. Normal adult and spinal cord-transected (SCT) rat bladders were stained with Ca2+- and voltage-sensitive dyes, and optical activity generated from intrinsic contractions was mapped from the mucosal surface of whole bladder sheets. Both normal adult and SCT rat bladders displayed intrinsic contractions, where normal bladders showed low-amplitude, high-frequency contractions with disorganized patterns of activity. In contrast, in the SCT animals there were high-amplitude, low-frequency contractions that displayed an organized spread of membrane potential and intracellular Ca2+. The difference in contractile activity was mirrored in the Ca2+ and membrane potential maps of bladder sheets. Normal bladders showed multiple initiation sites across the mucosal surface, whereas SCT bladders showed only one or two fixed initiation sites localized to the dome. The magnitude of intrinsic contractions could be enhanced by stretch or low-dose arecaidine (50 nM), a muscarinic-specific agonist. Partial removal of the mucosa decreased the amplitude of the intrinsic contractions and decreased the response to stretch or arecaidine. Optical mapping of mucosa-denuded sheets, where enhanced spontaneous activity was abolished, or application of 1 microM nifedipine to remove smooth muscle signals, but not the mucosal signals, shows that intrinsic activity in pathological bladders is driven by the mucosal layer. In summary, we suggest an urotheliogenic origin for intrinsic activity, where structures within the mucosal layer organize and thereby enhance intrinsic detrusor contractions.

The neural control of micturition

Micturition, or urination, occurs involuntarily in infants and young children until the age of 3 to 5 years, after which it is regulated voluntarily. The neural circuitry that controls this process is complex and highly distributed: it involves pathways at many levels of the brain, the spinal cord and the peripheral nervous system and is mediated by multiple neurotransmitters. Diseases or injuries of the nervous system in adults can cause the re-emergence of involuntary or reflex micturition, leading to urinary incontinence. This is a major health problem, especially in those with neurological impairment. Here we review the neural control of micturition and how disruption of this control leads to abnormal storage and release of urine.

The concept of neurogenic inflammation

Neurogenic inflammatory responses have recently been linked to both acute and chronic pathological conditions in the urinary tract. Neurogenic inflammation encompasses a series of vascular and non-vascular inflammatory responses, triggered by the activation of primary sensory neurons and the subsequent release of inflammatory neuropeptides, including substance P and calcitonin gene-related peptide. The reduction of neurogenic inflammatory responses may be key in the mode of action of the adrenergic alpha(1)-adrenoceptor antagonists used to treat lower urinary tract symptoms (LUTS). Indeed, the alpha(1)-adrenoceptor antagonist alfuzosin inhibits expression of the oncogene c-fos- a marker of nociceptive pathway activation - evoked by cyclophosphamide in rats. Capsaicin ameliorates urinary bladder symptoms through its stimulatory action on the transient receptor potential vanilloid 1 (TRPV1) calcium channel, resulting in desensitization of bladder sensory nerve terminals. Involvement of the TRP cation channel, subfamily A, member 1 (TRPA1) has also been reported in models of neurogenic inflammation and nociception promoted by the cyclophosphamide metabolite, acrolein. Blockade by alfuzosin demonstrates the beneficial effects of alpha(1)-adrenoceptor antagonists on neurogenic inflammation via the transient receptor potential family of ionic channels. Consequently, these drugs may have an important role in reducing LUTS.

Sensitization of pelvic afferent nerves in the in vitro rat urinary bladder-pelvic nerve preparation by purinergic agonists and cyclophosphamide pretreatment

Effects of purinergic agonists (alpha,beta-meATP and ATP) and cyclophosphamide-induced cystitis on bladder afferent nerve (BAN) activity were studied in an in vitro bladder-pelvic nerve preparation. Distension of the bladder induced spontaneous bladder contractions that were accompanied by multiunit afferent firing. Intravesical administration of 40 and 130 microM alpha,beta-meATP increased afferent firing from 27 +/- 3 to 53 +/- 6 and 61 +/- 2 spikes/s, respectively, but did not change the maximum amplitude of spontaneous bladder contractions. Electrical stimulation on the surface of the bladder elicited action potentials (AP) in BAN. alpha,beta-meATP decreased the voltage threshold from 9.0 +/- 1.2 to 3.5 +/- 0.5 V (0.15-ms pulse duration) and increased the area of the APs (82% at 80-V stimulus intensity). These effects were blocked by TNP-ATP (30 microM). ATP (2 mM) applied in the bath produced similar changes in BAN activity. These effects were blocked by bath application of PPADS (30 microM). Neither TNP-ATP nor PPADS affected BAN activity induced by distension of the bladder. Cystitis induced by pretreatment of the rats with cyclophosphamide (100 mg/kg ip) increased afferent firing in response to isotonic bladder distension (10-40 cmH(2)O), decreased the threshold, and increased the area of evoked APs. The increase in afferent firing at 10 cmH(2)O intravesical pressure was reduced 52% by PPADS. These results indicate that purinergic agonists acting on P2X receptors and cystitis induced by cyclophosphamide can increase excitability of the BANs.

Changes in T-type calcium channel and its subtypes in overactive detrusor of the rats with partial bladder outflow obstruction

AIMS

To investigate the activity of the T-type calcium channel (TCC) and the expression of its subtypes in overactive detrusor (OD) myocytes in rats after partial bladder outflow obstruction (PBOO).

METHODS

Thirteen male Wistar rats with OD after PBOO (OD group) and eight sham-operated rats (control group) were studied. The two groups were compared regarding the expression of TCC subtype genes by reverse transcription-polymerase chain reaction (RT-PCR) and the TCC kinetics and cell action potential by whole-cell patch-clamp.

RESULTS

The time course and density of the current were significantly higher in the OD cells than those in the control detrusor. Whole-cell patch-clamp analysis showed that the activation of TCCs in detrusor myocytes in the OD group was faster than the control group, but inactivation was almost the same in both groups, suggesting a significant enhancement of the Ca(2+) "window" current in the OD group. Patch-clamp recording of action potentials in the OD cells indicated an increase in excitability and a decrease in the repolarization interval. RT-PCR assay showed an abnormal expression of alpha1G subtype in the OD cells.

CONCLUSIONS

TCCs could be one of the crucial factors for the abnormal excitation in OD cells. The development of OD after PBOO presumably relates to the increase in TCC current in the bladder cells, the enhancement of the Ca(2+) "window" current for Ca(2+) inflow, the prolongation of the intracellular calcium oscillations, and the acceleration of the cell depolarization.

Resiniferatoxin and botulinum toxin type A for treatment of lower urinary tract symptoms

Resiniferatoxin (RTX) and botulinum toxin subtype A (BTX-A) are increasingly viewed as potential treatments for lower urinary tract symptoms (LUTS) refractory to conventional therapy. RTX, a capsaicin analogue devoid of severe pungent properties, acts by desensitizing the transient receptor potential vanilloid type 1 (TRPV1) receptor and inactivating C-fibers. BTX-A cleaves soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) proteins in afferent and efferent nerve endings, therefore impeding the fusion of synaptic vesicles with the neuronal membrane necessary for the release of neurotransmitters. In patients with neurogenic and idiopathic detrusor overactivity, RTX and BTX-A have been shown to increase the volume to first detrusor contraction, increase bladder capacity, and improve urinary incontinence and quality of life. Recent data also suggest a role for these neurotoxins in treating urgency, the primary symptom in overactive bladder (OAB) syndrome. Furthermore, experimental data strongly support the use of both neurotoxins in the treatment of pain and frequency in patients with interstitial cystitis/painful bladder syndrome (IC/PBS), although the results from available clinical trials for this use are still inconclusive. In spite of promising results overall, it should be made clear that the administration of these neurotoxins is still considered an experimental procedure and that more clinical studies are necessary before a license for their use will be issued by health authorities.

Changes of gap junctional cell-cell communication in overactive detrusor in rats

To evaluate the changes in intercellular communication through gap junctions in detrusor overactivity (DO), we studied 23 adult female Wistar rats with DO after partial outflow obstruction (DO group) and 13 sham-operated rats (control group). The two groups were compared by means of urodynamics, light and electron microscopy, expression of Cx40, Cx43, and Cx45 mRNA genes with RT-PCR, Cx43 protein with Western blot analysis, and functional intercellular communication with scrape loading dye transfer (SLDT) and fluorescence recovery after photobleaching (FRAP). The number of gap junctions and the expression of connexin mRNA and Cx43 protein were increased in DO rats, and intercellular communication through gap junctions increased after 6 wk of partial outflow obstruction as assessed with SLDT and FRAP techniques. The findings provide a theoretical rationale for using Cx43 antagonists and gap junction inhibitors in the treatment of patients with overactive detrusor secondary to partial bladder outflow obstruction.

Anticholinergic drugs versus other medications for overactive bladder syndrome in adults

BACKGROUND

Overactive bladder syndrome is defined as "urgency with or without urge incontinence, usually with frequency and nocturia". It is a common condition with significant economic and quality of life implications. While the condition's pathophysiology remains to be fully elucidated, pharmacotherapy is the main treatment option. Despite uncertainty as to drug treatment of choice, anticholinergics are increasingly being used in primary and secondary care settings. This review compares anticholinergic drugs with other types or classes of drugs for treating overactive bladder syndromes.

OBJECTIVES

To compare anticholinergic drugs with other types or classes of drugs for treating overactive bladder symptoms.

SEARCH STRATEGY

We searched the Cochrane Incontinence Group Specialised Trials Register (searched 20 December 2006) and the reference lists of relevant articles. No language or other limits were imposed.

SELECTION CRITERIA

All randomised and quasi-randomised controlled trials comparing anticholinergic drugs with other drugs for the treatment of overactive bladder symptoms. At least one arm of the study used an anticholinergic drug and at least one other arm used a non-anticholinergic drug.

DATA COLLECTION AND ANALYSIS

Two reviewers assessed the identified studies for eligibility and methodological quality and independently extracted data from the included studies. Data analysis was performed using RevMan software (version 4.2.8).

MAIN RESULTS

Twelve trials were included in the review. There were seven crossover trials and five parallel group studies. For the comparisons between anticholinergic drugs with tricyclic antidepressants, alpha adrenergic agonists, afferent nerve inhibitors, and calcium channel blocker a single trial was identified for each. Nine trials compared flavoxate with anticholinergics. There was no evidence of a difference in cure rates between anticholinergics and flavoxate. Adverse effects were more frequent in anticholinergic groups versus flavoxate groups (RR 2.28 95% CI 1.45 to 3.56). There was no strong evidence to favour either anticholinergic drugs or the comparators.

AUTHORS' CONCLUSIONS

Many of the drugs considered in trials in this review are no longer used in clinical practice (and this includes the most commonly tested - flavoxate). There is inadequate evidence as to determine whether any of the available drugs are better or worse than anticholinergic medications. Larger randomised controlled trials in clinical settings are required to further establish the role of these medications in the management of overactive bladder syndrome.

Properties of the major classes of mechanoreceptors in the guinea pig bladder

Sensory neurons represent an attractive target for pharmacological treatment of various bladder disorders. However the properties of major classes of mechano-sensory neurons projecting to the bladder have not been systematically established. An in vitro bladder preparation was used to examine the effects of a range of mechanical stimuli (stretch, von Frey hair stroking and focal compression of receptive fields) and chemical stimuli (1 mm alpha,beta-methylene ATP, hypertonic solutions (500 mm NaCl) and 3 microm capsaicin) during electrophysiological recordings from guinea pig bladder afferents. Four functionally distinct populations of bladder sensory neurons were distinguished by these stimuli. The first class, muscle mechanoreceptors, were activated by stretch but not by mucosal stroking with light (0.05-0.1 mN) von Frey hairs or by hypertonic saline, alpha,beta-methylene ATP or capsaicin. Removal of the urothelium did not affect their stretch-induced firing. The second class, muscle-mucosal mechanoreceptors, were activated by both stretch and mucosal stroking with light von Frey hairs or by hypertonic saline and by alpha,beta-methylene ATP, but not by capsaicin. Removal of the urothelium reduced their stretch- and stroking-induced firing. The third class, mucosal high-responding mechanoreceptors, were stretch-insensitive but could be activated by mucosal stroking with light von Frey hairs or by hypertonic saline, alpha,beta-methylene ATP and capsaicin. Stroking-induced firing was significantly reduced by removal of the urothelium. The fourth class, mucosal low-responding mechanoreceptors, were stretch insensitive but could be weakly activated by mucosal stroking with light von Frey hairs but not by hypertonic saline, alpha,beta-methylene ATP or capsaicin. Removal of the urothelium reduced mucosal stroking-induced firing. All four populations of afferents conducted in the C-fibre range and showed class-dependent differences in spike amplitude and duration. At least four functional classes of bladder mechanoreceptors can be readily distinguished by different mechanisms of activation and are likely to transmit different types of information to the central nervous system.

Damage to the bladder neck alters autonomous activity and its sensitivity to cholinergic agonists

OBJECTIVE

To identify and describe changes to the motor component of the motor/sensory system, which contributes to sensation during the filling phase of the micturition cycle, as a result of surgically induced bladder pathology, i.e. damage to the bladder neck and outlet obstruction.

MATERIALS AND METHODS

Adult male guinea pigs (294-454 g) were assigned initially into three groups: (i) normal guinea pigs with no surgical intervention (control, seven); (ii) guinea pigs which, with full surgical anaesthesia, had a silver ring implanted around the bladder neck (obstructed, 13); and (iii) guinea pigs operated to expose the bladder neck but with no implantation of a ring (sham, six). At 2-4 weeks after surgery the bladders were isolated, weighed and the pressure recordings used to identify autonomous activity.

RESULTS

The bladder weights in all operated groups, including the sham, were greater than controls. Bladder weights in the obstructed guinea pigs varied considerably, reflecting the degree of pathological change. Consequently, bladders from this group were divided into those with high (OBH) and those with low bladder weight (OBL). The mean (sd) amplitudes of the autonomous contractions were 1.1 (0.1), 10.8 (1.8), 11.4 (2.5) and 17.1 (4.0) cmH(2)O in control, sham, OBL and OBH bladders, respectively, indicating a progressive alteration in function with the pathology. The changes in the sham group suggested that the pathological changes were not the result of obstruction but damage to the bladder neck, the implantation of the silver rings exacerbating the damage. There were episodes of rapid phasic activity (bursts) in 10 of 13 of the ring-implanted bladders, and in two of six in the sham group, but never in controls. Neither the autonomous activity nor the bursts were affected by tetrodotoxin (1 microm) or atropine (3 microm) but they were abolished by noradrenaline (3 microm). In control bladders, adding the muscarinic agonist arecaidine produced a transient acceleration of phasic activity and increased the amplitude of the contractions. There was a similar acceleration of activity in all the operated groups but the concentrations needed to achieve an increase in frequency were significantly lower, the relative sensitivity to arecaidine being OBH >/= OBL > sham > control.

CONCLUSION

The mechanism involved in controlling the frequency of the motor component of the motor/sensory system, the 'pacemaker', appears to become progressively 'supersensitive' to cholinergic stimulation with the development of pathology. These observations are discussed in relation to the motor/sensory system and the origins of sensation in the bladder. The argument is proposed that damage to the bladder neck, not obstruction per se, results in altered nonmicturition activity which contributes to increased afferent output. In turn this contributes to the increased sensations of urge associated with bladder dysfunction. The cholinergic regulation of this altered 'pacemaker' might be the target for one of the therapeutic actions of anticholinergic drugs.

On the origin of bladder sensing: Tr(i)ps in urology

The mammalian TRP family consists of 28 channels that can be subdivided into 6 different classes: TRPV (vanilloid), TRPC (canonical), TRPM (Melastatin), TRPP (Polycystin), TRPML (Mucolipin), and TRPA (Ankyrin). TRP channels are activated by a diversity of physical (voltage, heat, cold, mechanical stress) or chemical (pH, osmolality) stimuli and by binding of specific ligands, enabling them to act as multifunctional sensors at the cellular level. Currently, a lot of scientific research is devoted to these channels and their role in sensing mechanisms throughout the body. In urology, there's a growing conviction that disturbances in afferent (sensory) mechanisms are highly important in the pathogenesis of functional problems. Therefore, the TRP family forms an interesting new target to focus on. In this review we attempt to summarize the existing knowledge about TRP channels in the urogenital tract. So far, TRPV1, TRPV2, TRPV4, TRPM8, and TRPA1 have been described in different parts of the urogenital tract. Although only TRPV1 (the vanilloid receptor) has been extensively studied so far, more evidence is slowly accumulating about the role of other TRP channels in the (patho)physiology of the urogenital tract.

Neural mechanisms of pelvic organ cross-sensitization

Clinical observations of viscerovisceral referred pain in patients with gastrointestinal and genitourinary disorders suggest an overlap of neurohumoral mechanisms underlying both bowel and urinary bladder dysfunctions. Close proximity of visceral organs within the abdominal cavity complicates identification of the exact source of chronic pelvic pain, where it originates, and how it relocates with time. Cross-sensitization among pelvic structures may contribute to chronic pelvic pain of unknown etiology and involves convergent neural pathways of noxious stimulus transmission from two or more organs. Convergence of sensory information from discrete pelvic structures occurs at different levels of nervous system hierarchy including dorsal root ganglia, the spinal cord and the brain. The cell bodies of sensory neurons projecting to the colon, urinary bladder and male/female reproductive organs express a wide range of membrane receptors and synthesize many neurotransmitters and regulatory peptides. These substances are released from nerve terminals following enhanced neuronal excitability and may lead to the occurrence of neurogenic inflammation in the pelvis. Multiple factors including inflammation, nerve injury, ischemia, peripheral hyperalgesia, metabolic disorders and other pathological conditions dramatically alter the function of directly affected pelvic structures as well as organs located next to a damaged domain. Defining precise mechanisms of viscerovisceral cross-sensitization would have implications for the development of effective pharmacological therapies for the treatment of functional disorders with chronic pelvic pain such as irritable bowel syndrome and painful bladder syndrome. The complexity of overlapping neural pathways and possible mechanisms underlying pelvic organ crosstalk are analyzed in this review at both systemic and cellular levels.

The Influence of Alpha1-Adrenoreceptors on Neuropeptide Release from Primary Sensory Neurons of the Lower Urinary Tract

OBJECTIVES

Adrenergic alpha(1)-receptors agonists and antagonists have been reported to increase and reduce, respectively, neurogenic inflammatory responses mediated by capsaicin-sensitive sensory neurons. However, the precise role and localization of the alpha(1)-adrenoceptors involved in these effects are not known.

METHODS

We have studied in the rat whether functional alpha(1)-adrenoreceptors are expressed in primary sensory neurons, and whether they regulate neurogenic inflammation and nociceptive responses in the urinary bladder.

RESULTS

The alpha(1)-adrenoreceptor agonist phenylephrine (1 micromol/l) (1) mobilized intracellular Ca(2+) in cultured lumbar and sacral dorsal root ganglia neurons, (2) caused the release of substance P (SP) from terminals of capsaicin-sensitive sensory neurons from the lumbar enlargement of the dorsal spinal cord and urinary bladder, and (3) increased plasma protein extravasation in the urinary bladder. All these effects were abolished by the alpha(1)-adrenoceptor antagonist alfuzosin (10 micromol/l). Furthermore, alfuzosin (30 microg/kg, i.v.) partially, but significantly, inhibited cyclophosphamide-induced plasma protein extravasation in the rat urinary bladder. Phenylephrine-induced Ca(2+) mobilization in cultured dorsal root ganglia neurons was exaggerated by pretreating the rats in vivo with cyclophosphamide. Finally, cyclophosphamide increased c-fos expression in the rat lumbar spinal cord. Also these in vitro and in vivo effects were inhibited by pretreatment with alfuzosin.

CONCLUSIONS

Alpha(1)-adrenoceptors are functionally expressed by capsaicin-sensitive, nociceptive, primary sensory neurons of the rat urinary tract, and their activation may contribute to signal irritative and nociceptive responses arising from the urinary tract. It is possible that, at least, part of the beneficial effects of alpha(1)-adrenoceptor antagonists in the amelioration of storage symptoms in the lower urinary tract derives from their inhibitory effect on neurogenic inflammatory responses.

A survey of commonalities relevant to function and dysfunction in pelvic and sexual organs

Micturition, defecation and sexual function are all programmed through spinal reflexes that are under descending control from higher centres. Interaction between these reflexes can clearly be perceived, and evidence is accumulating the dysfunction in one reflex is often associated with dysfunction in another. In this article, we describe some of the basic properties and neural control of the smooth muscles mediating the reflexes, reviewing the common features that underlie these reflex functions, and what changes may be responsible for dysfunction. We propose that autonomic control within the pelvis predisposes pelvic and sexual organs to crosstalk, with the consequence that diseases and conditions of the pelvis are subject to convergence on a functional level. It should be expected that disturbance of the function of one system will inevitably impact adjacent systems.

Developments in the pharmacotherapy of the overactive bladder

PURPOSE OF REVIEW

The overactive bladder is a common and distressing condition that has a significant impact on the quality of life of many people worldwide. Anticholinergics remain the first line in pharmacotherapy, however the use of these agents is hindered by adverse effects and limited efficacy. Thus there is a need for more effective treatments. Recently, there has been a move towards targeting novel pathways thought to play a role in overactivity. This review aims to provide an insight into the recent developments in pharmacotherapy of the overactive bladder.

RECENT FINDINGS

With recent advances in our understanding of the basic science of the overactive bladder it is becoming clear that the control of bladder functioning is far more complex than previously believed. Peripherally, a prominent role has emerged for the urothelium and the underlying suburothelium in mechanosensory control, and the role of afferent pathways in pathophysiology is increasingly recognized.

SUMMARY

Recent research has highlighted several potential targets for treatment of the overactive bladder, particularly within the mechanosensory pathways. With the exception of botulinum toxin, however, few new therapies have emerged showing clinical benefits. A clearer understanding of the pathophysiology of the bladder will hopefully lead to more effective and tolerated treatments.

[Epidemiology and etiology of urinary incontinence in the elderly]

Urinary incontinence is an important and common health problem, whose prevalence increases with age. Often quality of life is clearly affected for persons concerned. In the group of elderly individuals (> or =60 years of age) 19.3% of women and 10.4% of men report urinary incontinence. Women most frequently describe urinary stress incontinence followed by incontinence with urge symptoms (urge incontinence, mixed incontinence). In men urinary incontinence without any symptoms of stress or urge incontinence is most common followed by incontinence with urge symptoms and stress incontinence. Urinary incontinence in the elderly is rarely due to a single reason but rather due to multiple factors. In urinary stress incontinence, a differentiation can be made between mechanical and functional problems of the sphincter mechanism caused by myogenic, neurogenic, hormonal, or iatrogenic factors as well as changes in connective tissue. In urinary incontinence with urge symptoms, geriatric detrusor function is mostly affected by neurogenic, myogenic, or urothelial factors whereas the detrusor muscle shows characteristic ultrastructural changes. In chronic urinary retention with consecutive urinary incontinence, especially in men infravesical obstruction is more often the reason than a geriatric bladder dysfunction.

TRPs in bladder diseases

This review attempts to provide an overview of the current knowledge of TRP proteins and their possible role in bladder function and disease. At present, there are 28 transient receptor potential (TRP) channels (subdivided into 7 categories or families) which are involved in a number of functions [G.A. Hicks, TRP channels as therapeutic targets: hot property, or time to cool down? Neurogastroenterology and Motility 18, (2006) 590-594., J.D. Levine, N. Alessandri-Haber, TRP channels: targets for the relief of pain, Biochimica et Biophysica Acta 1772, (2007) 989-1003.]. Of those belonging to the group 1 subfamily, a number of TRPV, TRPM and TRPA proteins associated with osmoregulation, thermal, chemical and mechanical signaling mechanisms have been shown to be expressed within the lower urinary tract. Though the biological role of many of these channels in urinary bladder function still remains elusive, TRPV1 is by far the best characterized and is thought to be involved in a number of bladder disorders [A. Szallasi, P.M. Blumberg, Vanilloid (Capsaicin) Receptors and Mechanisms, Pharmacological Reviews 51, (1999) 150-221., I. Nagy, P. Santha, G. Jansco, L. Urban, The role of the vanilloid (capsaicin) receptor (TRPV1) in physiology and pathology, European Journal of Pharmacology 500, (2004) 351-369.].

Anticholinergic drugs versus other medications for overactive bladder syndrome in adults

BACKGROUND

Overactive bladder syndrome is defined as "urgency with or without urge incontinence, usually with frequency and nocturia". It is a common condition with significant economic and quality of life implications. While the condition's pathophysiology remains to be fully elucidated, pharmacotherapy is the main treatment option. Despite uncertainty as to drug treatment of choice, anticholinergics are increasingly being used in primary and secondary care settings. This review compares anticholinergic drugs with other types or classes of drugs for treating overactive bladder syndromes.

OBJECTIVES

To compare anticholinergic drugs with other types or classes of drugs for treating overactive bladder symptoms.

SEARCH STRATEGY

We searched the Cochrane Incontinence Group Specialised Trials Register (searched 20 December 2006) and the reference lists of relevant articles. No language or other limits were imposed.

SELECTION CRITERIA

All randomised and quasi-randomised controlled trials comparing anticholinergic drugs with other drugs for the treatment of overactive bladder symptoms. At least one arm of the study used an anticholinergic drug and at least one other arm used a non-anticholinergic drug.

DATA COLLECTION AND ANALYSIS

Two reviewers assessed the identified studies for eligibility and methodological quality and independently extracted data from the included studies. Data analysis was performed using RevMan software (version 4.2.8).

MAIN RESULTS

Thirteen trials were included in the review. There were eight crossover trials and five parallel group studies. For the comparisons between anticholinergic drugs with tricyclic antidepressants, alpha adrenergic agonists, afferent nerve inhibitors, and calcium channel blocker a single trial was identified for each. Ten trials compared flavoxate with anticholinergics. There was no evidence of a difference in cure rates between anticholinergics and flavoxate. Adverse effects were more frequent in anticholinergic groups versus flavoxate groups (RR 2.28 95% CI 1.45 to 3.56). There was no strong evidence to favour either anticholinergic drugs or the comparators.

AUTHORS' CONCLUSIONS

Many of the drugs considered in trials in this review are no longer used in clinical practice (and this includes the most commonly tested - flavoxate). There is inadequate no evidence as to whether any of the available is better or worse than anticholinergic medications. Larger randomised controlled trials in clinical settings are required to further establish the role of these other medications in the management of overactive bladder syndrome.

Involvement of reflex urethral closure mechanisms in urethral resistance under momentary stress condition induced by electrical stimulation of rat abdomen

A novel method for evaluating the urethral resistance during abrupt elevation of abdominal pressure was developed in spinalized female rats under urethane anesthesia. Electrical stimulation of abdominal muscles for 1 s induced increases in both the intra-abdominal and the intravesical pressure in a stimulus-dependent manner, and the bladder response was almost lost when the abdomen was opened. The lowest intravesical pressure during electrical stimulation that induced fluid leakage from the urethral orifice (leak point pressure) and the maximal intravesical pressure without urine leakage below the leak point pressure were evaluated as the indexes of urethral resistance. Lower urethral resistance was obtained in the rats whose pelvic nerves or somatic nerves containing pudendal nerves and nerves to iliococcygeus/pubococcygeus muscles were transected bilaterally. In contrast, transection of bilateral hypogastric nerves showed smaller effects. Duloxetine, a drug for stress urinary incontinence, enlarged the reflex urethral closing contractions that were induced by an increase in intravesical pressure and measured using a microtip transducer catheter in the middle urethra. This drug also increased the urethral resistance (leak point pressure), whereas it did not show any effect in the rats whose pelvic nerves were bilaterally transected, showing that the augmentation of the reflex urethral closure by the drug resulted in the elevation of the urethral resistance. From these findings, it was concluded that during momentary elevation of abdominal pressure, the reflex urethral closure mechanisms via bladder-spinal cord-urethral sphincter and pelvic floor muscles greatly contribute to the increase in the urethral resistance to prevent the urinary incontinence.

Urethral and Bladder Current Perception Thresholds: Normative Data in Women

PURPOSE

Given increased evidence of sensory dysfunction in lower urinary tract pathology, we determined normative current perception threshold values in the lower urinary tract of asymptomatic women.

MATERIALS AND METHODS

After receiving institutional review board approval women without lower urinary tract symptoms underwent current perception threshold testing of the urethra and bladder using a Neurometer constant current stimulator. Current perception threshold values were determined at 3 frequencies, including 2,000 Hz (corresponding to A-beta fibers), 250 Hz (corresponding to A-delta fibers) and 5 Hz (corresponding to C fibers).

RESULTS

A total of 48 women with a mean age of 38 years (range 23 to 67) underwent current perception threshold testing. Normative values were established for the urethra and bladder at 2,000, 250 and 5 Hz. Median urethral current perception thresholds at 2,000, 250 and 5 Hz were 1.2 (IQR 0.76-1.5), 0.45 (IQR 0.33-0.56) and 0.11 mA (IQR 0.07-0.24), respectively. Median bladder current perception thresholds at 2,000, 250 and 5 Hz were 4.1 (IQR 2.0-6.3), 2.3 (IQR 0.87-5.5) and 1.4 mA (IQR 0.22-2.9), respectively. Urethral and bladder current perception thresholds increased significantly with subject age at all 3 frequencies (p<0.0005). Prior pelvic surgery was associated with an increased bladder current perception threshold at all 3 frequencies (p<0.005) but not with the urethral current perception threshold.

CONCLUSIONS

We report urethral and bladder current perception thresholds for a large sample of asymptomatic women. These reference values may help elucidate changes in afferent nerve function in women with lower urinary tract dysfunction.