Focal changes in nerve, muscle and connective tissue in normal and unstable human bladder

Administration of leuprolide acetate, a GnRH agonist, improves urodynamic parameters in ovariectomized rats

AIM

To evaluate the effects of a treatment with leuprolide acetate (LA) on bladder overactivity as well as the expression of gonadotropin releasing hormone receptor (GnRH-R), and neurofilaments NF68 and NF200 in female rats with overactive bladder induced by castration.

METHODS

Changes in the urodynamic parameters were determined in SHAM, ovariectomized (OVX) and ovariectomized rats treated with LA (OVX-LA). A semi-quantitative analysis for the expression pattern of GnRH-R and neurofilaments NF68 and NF200 were determined.

RESULTS

Forty-three days after ovariectomy, rats from the OVX group have significant lower values for intercontractile interval (ICI) and compliance (C); as well as higher values for basal bladder pressure (BP) and frequency of non-voiding contractions (NVC). The systemic application of LA increased voiding volume (Vv) and pressure threshold (ThP) in the OVX-LA animals. The application of LA reduced the high frequency of NVC in the OVX rats. No significant differences were found for Vv and NVCs between the OVX-LA vs SHAM groups. At the mid part of the bladder, the presence of GnRH-R was evidenced in the urothelium of the SHAM group. The OVX animals showed different pattern of immunolabeling for GnRH-R as well as for neurofilaments NF200 and NF68, whereas in the OVX-LA group the immunofluorescence pattern was similar to the one seen in SHAM bladders (P < 0.05 for OVX vs OVX + LA).

CONCLUSIONS

the results suggest that systemic application of LA can improve bladder dysfunction in castrated rats, and perhaps considered as a treatment for overactive bladder conditions secondary to menopause.

Changes in Management of Poorly Compliant Bladder in Botulinum Toxin A Era

Bladder compliance is a measure of distensibility. Maladies such as myelodysplasia, myelomeningocele, spinal cord injury, multiple sclerosis and obstructive uropathy are known to decrease bladder compliance. Decrease in bladder compliance is a characteristic of neurogenic bladders. The pathophysiology of bladder compliance is complex but ultimately leads to high pressure during filling and storage phases. These high pressures lead to renal impairment, incontinence, and recurrent urinary tract infections. This review presents management of poorly compliant bladders with onabotulinumtoxinA.

Effects of nitric oxide inhibitors in mice with bladder outlet obstruction

PURPOSE

To investigate the lower urinary tract changes in mice treated with L-NAME, a non-selective competitive inhibitor of nitric oxide synthase (NOS), or aminoguanidine, a competitive inhibitor of inducible nitric oxide synthase (iNOS), after 5 weeks of partial bladder outlet obstruction (BOO), in order to evaluate the role of constitutive and non-constitutive NOS in the pathogenesis of this experimental condition.

MATERIALS AND METHODS

C57BL6 male mice were partially obstructed and randomly allocated into 6 groups: Sham, Sham + L-NAME, Sham + aminoguanidine, BOO, BOO + L-NAME and BOO + aminoguanidine. After 5 weeks, bladder weight was obtained and cystometry and tissue bath contractile studies were performed.

RESULTS

BOO animals showed increase of non-voiding contractions (NVC) and bladder capacity, and also less contractile response to Carbachol and Electric Field Stimulation. Inhibition of NOS isoforms improved bladder capacity and compliance in BOO animals. L-NAME caused more NVC, prevented bladder weight gain and leaded to augmented contractile responses at muscarinic and electric stimulation. Aminoguanidine diminished NVC, but did not avoid bladder weight gain in BOO animals and did not improve contractile responses.

CONCLUSION

It can be hypothesized that chronic inhibition of three NOS isoforms in BOO animals leaded to worsening of bladder function, while selective inhibition of iNOS did not improve responses, what suggests that, in BOO animals, alterations are related to constitutive NOS.

Urinary Biomarkers in Women with Refractory Urgency Urinary Incontinence Randomized to Sacral Neuromodulation versus OnabotulinumtoxinA Compared to Controls

PURPOSE

We measured urinary biomarker levels in women with refractory urgency urinary incontinence and controls at baseline and 6 months after treatment with sacral neuromodulation or intradetrusor injection of onabotulinumtoxinA. We also assessed the association of baseline biomarkers with posttreatment urgency urinary incontinence episodes and overactive bladder symptom bother outcomes.

MATERIALS AND METHODS

First morning urine samples were collected from consented trial participants and age matched women without urgency urinary incontinence. Biomarkers reflecting general inflammation, neuroinflammation, afferent neurotransmitters and tissue remodeling were measured using standardized enzyme-linked immunosorbent assay and activity assays as appropriate. Symptom bother was assessed by the overactive bladder questionnaire and urgency urinary incontinence episodes were determined by bladder diary. Linear models were used to examine differences in mean biomarker levels and the change in urgency urinary incontinence episodes and symptom bother between baseline and 6 months. Modest evidence of a potential association was represented by p ≤0.01 and p ≤0.004 represented moderate evidence of an association with outcomes.

RESULTS

Baseline biomarker levels differed little between cases and controls except tropoelastin (p = 0.001) and N-terminal telopeptide collagen type 1 (p <0.001). Changes in biomarker levels 6 months after intervention included decreases in collagenase (p <0.001) in both treatment groups and increases in interleukin-8 (p = 0.002) and matrix metalloprotease-9 (p <0.001) in the onabotulinumtoxinA group. Higher baseline calcitonin gene-related peptide across both treatments (p = 0.007) and nerve growth factor in the onabotulinumtoxinA arm (p = 0.007) were associated with less reduction in overactive bladder symptom bother.

CONCLUSIONS

Refractory urgency urinary incontinence is a complex condition. These data suggest that matrix remodeling and neuropeptide mediation may be involved in its pathophysiological mechanisms and response to treatment.

Prostatic Artery Embolization (PAE) for Symptomatic Benign Prostatic Hyperplasia (BPH): Part 1, Pathological Background and Clinical Implications

Pathological features of benign prostatic hyperplasia (BPH) dictate various responses to prostatic artery embolization (PAE). Typically, BPH originates in the transition zone and periurethral region, where should be considered the primary target area in PAE procedures. Given that histological heterogeneity of components in hyperplasia nodules, epithelial or stromal, identifying the more responsive nodules to PAE will have clinical implications. Since some lower urinary tract symptoms (LUTS) in patients with BPH are usually related to bladder outlet obstruction-induced changes in bladder function rather than to outflow obstruction directly, proper selection of candidate patients prior to PAE is of great clinical importance. BPH is a typical chronic progressive condition, suggesting PAE could aim not only to relieve LUTS but also to delay or prevent the clinical progression. Awareness of the pathological background of BPH is essential for interventional radiologists to improve clinical outcomes and develop new treatment strategies in clinical practice of PAE.

[Physiopathology of overactive bladder syndrome]

The pathophysiology of OAB is complex, multifactorial and still largely unknown. Several pathophysiological mechanisms have been highlighted that may play a different role in different patient groups. There are now experimental evidences that support both the myogenic and neurogenic hypothesis, but in recent years the "integrative" hypothesis has been gaining more and more acceptance, where a disruption in the multiple interactions between different cell types (neurons, urothelium, interstitial cells, myocytes) and network functions represent a central element of lower urinary tract dysfunctions. Of utmost importance, a disorder in the urothelial sensory function and in the urothelial/suburothelial non-neural cholinergic system, favored by age and comorbidities, appears to be crucial for the development of the OAB. Neuroplastic and detrusor changes in OAB are broadly similar to those observed in bladders exposed to outlet obstruction, neuropathies, inflammation or aging, and may be driven by a common urothelial dysfunction. Several signaling substances and their receptors were found to be involved in central pathways of bidirectional communication between the different cell types in the bladder, and were shown to be modified in several animal models of OAB as well as in human models, indicating new potential therapeutic targets.

Local Change in Urinary Bladder Contractility Following CNS Dopamine Denervation in the 6-OHDA Rat Model of Parkinson's Disease

BACKGROUND

Urinary problems, including urinary frequency, urgency, and nocturia are some of the non-motor symptoms that correlate most with poor quality of life in Parkinson's disease. However, the mechanism behind these symptoms is poorly understood, in particular regarding peripheral bladder pathophysiology following dopamine degeneration.

OBJECTIVE

In this study, we compared the contractile responsiveness of urinary bladder from the 6-OHDA unilateral rat model of Parkinson's disease with that of normal untreated animals.

METHODS

The contractility of the urinary detrusor muscle was evaluated in bladder strip preparations using electrical field stimulation, and muscarinic and purinoceptor stimulations in an vitro organ bath setup.

RESULTS

Our data show that the overall contractile response following electrical field stimulation was significantly higher (43% at maximum contraction by 20-40 Hz stimulation) in the 6-OHDA-lesioned rats as compared to control animals. This increase was associated with a significant increase in the cholinergic contractile response, where the muscarinic agonist methacholine produced a 44% (at 10 -4 M concentration) higher response in the 6-OHDA-treated rats as compared to controls with a significant left-shift of the dose response. This indicates an altered sensitivity of the muscarinic receptor system following the specific central 6-OHDA-induced dopamine depletion. In addition a 36% larger contraction of strips from the 6-OHDA animals was also observed with purinoceptor activation using the agonist ATP (5×10 -3 M) during atropine treatment.

CONCLUSIONS

Our data shows that it is not only the central dopamine control of the micturition reflex that is altered in Parkinson's disease, but also the local contractile function of the urinary bladder. The current study draws attention to a mechanism of urinary dysfunction in Parkinson's disease that has previously not been described.

Alterations of the myovesical plexus of the human overactive detrusor

Objectives. The human bladder shows spontaneous autonomous activity. Detrusor overactivity could be seen as a consequence of exaggerated autonomous activity. Interstitial cells (ICs) play a potential role in coordination of autonomous activity. As it is suggested that changes in ICs coexist with detrusor overactivity (DO), we investigated possible alterations to human bladder ICs. Methods. Biopsies were obtained from 23 patients and were categorized into four groups: genuine stress incontinence (without DO) (n = 5), neurogenic disease with DO (n = 6), bladder outlet obstruction with DO (n = 6), or idiopathic DO (n = 6). Specimens were processed to investigate expression of N-cadherin and PGP9.5. N-cadherin expression was semiquantitatively analyzed and correlated to PG9.5 expression and bladder wall morphology. Results. The population of cells expressing N-cadherin is altered in the overactive detrusor, making no difference between the sources of DO. Punctate distribution of morphological changes was found and downregulation of PGP9.5 expression seemed to coexist with upregulation of N-cadherin expression in the detrusor layer. Conclusions. The population of N-cadherin+ cells of the interstitial compartment of the human bladder has the ability to proliferate. As this proliferation seems to coexist with denervation, it could be possible that a highly developed network of interstitial cells replaces the loss of innervation in overactive detrusor.

Autonomic nervous control of the urinary bladder

The autonomic nervous system plays an important role in the regulation of the urinary bladder function. Under physiological circumstances, noradrenaline, acting mainly on β(3) -adrenoceptors in the detrusor and on α(1) (A) -adrenoceptors in the bladder outflow tract, promotes urine storage, whereas neuronally released acetylcholine acting mainly on M(3) receptors promotes bladder emptying. Under pathophysiological conditions, however, this system may change in several ways. Firstly, there may be plasticity at the levels of innervation and receptor expression and function. Secondly, non-neuronal acetylcholine synthesis and release from the urothelium may occur during the storage phase, leading to a concomitant exposure of detrusor smooth muscle, urothelium and afferent nerves to acetylcholine and noradrenaline. This can cause interactions between the adrenergic and cholinergic system, which have been studied mostly at the post-junctional smooth muscle level until now. The implications of such plasticity are being discussed.

CXC-type chemokines promote myofibroblast phenoconversion and prostatic fibrosis

Recent studies from our group suggest that extracellular matrix (ECM) deposition and fibrosis characterize the peri-urethral prostate tissues of some men suffering from Lower Urinary Tract Symptoms (LUTS) and that fibrosis may be a contributing factor to the etiology of LUTS. Fibrosis can generally be regarded as an errant wound-healing process in response to chronic inflammation, and several studies have shown that the aging prostate tissue microenvironment is rich with inflammatory cells and proteins. However, it is unclear whether these same inflammatory proteins, particularly CXC-type chemokines, can mediate myofibroblast phenoconversion and the ECM deposition necessary for the development of prostatic tissue fibrosis. To examine this, immortalized and primary prostate stromal fibroblasts treated with TGF-β1, CXCL5, CXCL8, or CXCL12 were evaluated morphologically by microscopy, by immunofluorescence and qRT-PCR for αSMA, collagen 1, vimentin, calponin, and tenascin protein and transcript expression, and by gel contraction assays for functional myofibroblast phenoconversion. The results of these studies showed that that immortalized and primary prostate stromal fibroblasts are induced to express collagen 1 and 3 and αSMA gene transcripts and proteins and to undergo complete and functional myofibroblast phenoconversion in response to CXC-type chemokines, even in the absence of exogenous TGF-β1. Moreover, CXCL12-mediated myofibroblast phenoconversion can be completely abrogated by inhibition of the CXCL12 receptor, CXCR4. These findings suggest that CXC-type chemokines, which comprise inflammatory proteins known to be highly expressed in the aging prostate, can efficiently and completely mediate myofibroblast phenoconversion and may thereby promote fibrotic changes in prostate tissue architecture associated with the development and progression of male lower urinary tract dysfunction.

Altered bladder function in elastin-deficient mice at baseline and in response to partial bladder outlet obstruction

OBJECTIVE

• To examine functional and molecular changes of the bladders from elastin-haploinsufficient mice (Eln(+/-) ) at baseline as well as in response to partial bladder outlet obstruction (pBOO).

MATERIALS AND METHODS

• Female Eln(+/-) and wild type (Wt) mice (3-4 months old) were studied. • The bladder elastin content was quantified by measuring desmosine. • Mice were divided into two groups to undergo surgery to create pBOO or to undergo sham surgery. Three days after surgery, bladder function was evaluated by in vivo cystometry, and the contractile response of bladder strips exposed to electrical field stimulation (EFS) and carbachol was examined by ex vivo myography.

RESULTS

• The Eln(+/-) -sham mice had a 33.6% decrease in bladder elastin compared with Wt-sham mice. • Cystometry showed significantly decreased bladder compliance and capacity in Eln(+/-) -sham vs Wt-sham mice; pBOO increased bladder compliance and capacity to a greater extent in Eln(+/-) mice compared with Wt mice. • Bladder strips from Eln(+/-) -sham mice showed a significantly heightened contractile response to both EFS and carbachol compared with Wt-sham mice. • A significantly increased contractile response to carbachol was detected in Wt-pBOO vs Wt-sham but not between Eln(+/-) -pBOO and Eln(+/-) -sham mice.

CONCLUSION

• The results that elastin-deficient mice had decreased bladder compliance and capacity and increased bladder contractility; and that Wt-pBOO mice showed an enhanced contractile response to carbachol, but Eln(+/-) -pBOO mice did not, suggest that elastin is critical for normal bladder function and is involved in bladder response to pBOO.

Overactive bladder in males

The prevalence of overactive bladder (OAB) symptoms is considerable in both men and women and the impact on quality of life (QOL) is equally substantial. Ironically, despite nearly equal prevalence, OAB symptoms in men are infrequently treated, and often with medical therapies aimed at bladder outlet obstruction (BOO). In this review, we examine the pathophysiology of OAB and its evaluation in the context of benign prostatic hypertrophy and concomitant BOO. We then consider the efficacy and safety of individual therapeutic options for lower urinary tract symptoms in men, focusing on the mainstays of medical therapy: α-adrenergic blockers, 5-α reductase inhibitors, and antimuscarinic agents. Finally, we aim to comment on new therapeutic strategies and targets that may one day be available for the treatment of male OAB.

Adherence junctions and cadherin-11 in normal and overactive human detrusor smooth muscle cells

PURPOSE

We investigated whether analysis of adherence junctions in human detrusor could be used as a diagnostic tool to determine detrusor overactivity.

MATERIALS AND METHODS

We characterized the protein composition of adherence junctions in the human bladder using cadherin-11 since our group previously found that cadherin-11 could be an integral structural protein of adherence junctions. We obtained a total of 46 biopsies from 23 patients categorized into 4 groups, including 5 who were normal, and 6 each with neurogenic disease with detrusor overactivity, bladder outlet obstruction with detrusor overactivity and idiopathic detrusor overactivity. Specimens were processed to study cadherin-11 expression using combined immunohistochemical and immunogold electron microscopy techniques. Cadherin-11 expression was semiquantitatively analyzed and correlated to muscle fascicle structure and collagen in the extracellular spaces.

RESULTS

Immunogold labeling showed highly specific cadherin-11 expression at adherence junctions in detrusor smooth muscle cells. During immunohistochemical staining a wide variety of cadherin-11 expression and fascicle structure was found in the same specimen. No correlation was noted between detrusor overactivity and cadherin-11 expression. However, cadherin-11 seemed to be down-regulated with intercellular space widening and collagenosis.

CONCLUSIONS

Cadherin-11 is an integral structural protein of the adherence junction. Defects in the overactive detrusor are highly punctate. Quantitative analysis of adherence junctions using biopsy cannot replace urodynamic evaluation as a predictor of detrusor overactivity in the human bladder.

Muscarinic acetylcholine receptors in the urinary tract

Muscarinic receptors comprise five cloned subtypes, encoded by five distinct genes, which correspond to pharmacologically defined receptors (M(1)-M(5)). They belong to the family of G-protein-coupled receptors and couple differentially to the G-proteins. Preferentially, the inhibitory muscarinic M(2) and M(4) receptors couple to G(i/o), whereas the excitatory muscarinic M(1), M(3), and M(5) receptors preferentially couple to G(q/11). In general, muscarinic M(1), M(3), and M(5) receptors increase intracellular calcium by mobilizing phosphoinositides that generate inositol 1,4,5-trisphosphate (InsP3) and 1,2-diacylglycerol (DAG), whereas M(2) and M(4) receptors are negatively coupled to adenylyl cyclase. Muscarinic receptors are distributed to all parts of the lower urinary tract. The clinical use of antimuscarinic drugs in the treatment of detrusor overactivity and the overactive bladder syndrome has focused interest on the muscarinic receptors not only of the detrusor, but also of other components of the bladder wall, and these have been widely studied. However, the muscarinic receptors in the urethra, prostate, and ureter, and the effects they mediate in the normal state and in different urinary tract pathologies, have so far not been well characterized. In this review, the expression of and the functional effects mediated by muscarinic receptors in the bladder, urethra, prostate, and ureters, under normal conditions and in different pathologies, are discussed.

Partial urethral obstruction: ATF3 and p-c-Jun are involved in the growth of the detrusor muscle and its motor innervation

OBJECTIVE

Infravesical obstruction leads to growth of urinary bladder smooth-muscle cells. The ganglion cells innervating the bladder muscle also increase in size. Stretch of detrusor muscle cells rapidly activates c-Jun NH₂-terminal kinase (JNK), which phosphorylates the transcription factor c-Jun, and stimulates the synthesis of the cotranscription factor ATF3. The aim of the study was to determine whether ATF3 and p-c-Jun were involved in growth of bladder smooth-muscle and ganglion cells.

MATERIAL AND METHODS

The urethra was partially obstructed in female rats. After 3 days or 10 weeks bladders were weighed, fixated and cut for immunohistochemistry to demonstrate ATF3 and p-c-Jun. Ganglia were processed separately. Unoperated and sham-operated rats were used as controls.

RESULTS

There was no ATF3 or p-c-Jun in control detrusor muscle. After 3 days of obstruction bladder weight had nearly doubled. Almost all nuclei in the detrusor showed immunofluorescence for ATF3 and p-c-Jun. After 10 weeks bladder weight had increased 10-fold. Almost all detrusor nuclei still showed p-c-Jun, but few had ATF3 activity. In control ganglia there was no ATF3 and only faint nuclear p-c-Jun activity. After 3 days of obstruction the ganglion cells had increased in size and many nuclei showed intense immunofluorescence for ATF3 and p-c-Jun. After 10 weeks the ganglion cell size had increased further. There was no ATF3 activity and no more p-c-Jun than in control ganglia.

CONCLUSION

ATF3 and p-c-Jun seem to be involved in the growth of the detrusor muscle and its motor innervation following infravesical outlet obstruction.

Vardenafil-induced relaxation and cyclic nucleotide levels in normal and obstructed rat urinary bladder

OBJECTIVE

To study the effects of the phosphodiesterase-5 inhibitor, vardenafil, on contraction and cyclic nucleotide levels in isolated detrusor preparations with and without mucosa, from control rats and rats with partial urethral obstruction (PUO) and intact mucosa.

MATERIALS AND METHODS

Female Sprague-Dawley rats were divided into groups subjected to PUO for 14 days (six), and sham-operated control rats (12). Detrusor preparations were mounted in organ baths and effects of increasing concentrations of vardenafil (1 nm to 100 microm) assessed on carbachol-activated (1 microm) preparations, and on contractions induced by transmural activation of nerves (electrical field stimulation, EFS). Levels of cGMP and cAMP were determined using radioimmunoassays.

RESULTS

Vardenafil caused concentration-dependent relaxations of carbachol-contracted detrusor, the mean (sd) of which at 100 microm was 91 (4)% in control and 100% in PUO rats. The -log 50% inhibitory concentration (IC(50)) was 4.41 (0.08) and 4.73 (0.05) (P < 0.01), respectively. Removing the mucosa increased the relaxant effect of vardenafil at 1-10 microm (P < 0.05) although -log IC(50) values were unaffected compared to the control. The cGMP levels ( pmol/mg protein) in control preparations increased from 2.5 (0.6) to 5.0 (0.8), and from 1.4 (0.2) to 7.2 (1.3) in obstructed bladders. In mucosa-denuded preparations the cGMP content increased from 0.6 (0.1) to 1.6 (0.4) in response to vardenafil. In control rats, the levels of cAMP increased from 12.8 (2.5) to 18.9 (0.9) (P < 0.05) after vardenafil. In mucosa-denuded preparations the cAMP levels after vardenafil increased from 16.5 (2.11) to 37.8 (3.4) (P < 0.01). In PUO bladders, the tissue content of cAMP increased from 12.6 (2.4) to 20.6 (3.4) (P < 0.01). Vardenafil concentration-dependently inhibited nerve-induced contractions in all groups studied. At 100 microm 19 (3)% of the control contraction remained, vs 8 (1)% for preparations from obstructed rats, and 11 (4)% in mucosa-denuded preparations.

CONCLUSION

In normal rats, vardenafil relaxed carbachol- and inhibited EFS-induced contractions of detrusor preparations with and without urothelium, and in PUO rats with urothelium. Relaxations were accompanied by increases in both cAMP and cGMP content. It is proposed that vardenafil-induced relaxation of rat detrusor, also in obstructed and mucosa-denuded preparations, is mediated via cAMP.

Decellularization and sterilization of porcine urinary bladder matrix for tissue engineering in the lower urinary tract

BACKGROUND

Several synthetic and natural matrices have been described for tissue engineering of bladder but there is little information on the effects of processing on their subsequent mechanical performance or interaction with human cells.

AIM

Our aim was to assess the effects of delamination, decellularization and sterilization on the mechanical properties of porcine urinary bladder matrix (UBM) and to then assess the ability of the UBM to act as a scaffold for reconstruction with human bladder cells.

METHODS

A total of 20 porcine bladders were assessed before and after mechanical delamination and four porcine bladders were followed at every stage through a comparison of several decellularization and terminal sterilization methodologies examining histological and mechanical characteristics. The sterile UBM was seeded with normal human urothelial and bladder stromal cells either as a simultaneous coculture, or with stromal cells followed by urothelial cells.

RESULTS

Mechanical delamination, physical rinsing of the resulting bladder stroma in hypotonic buffer, 0.1% sodium dodecyl sulfate solution and 0.1% peracetic acid resulted in an UBM with acceptable mechanical properties capable of supporting urothelial and bladder stromal cells. Terminal sterilization with ethylene oxide resulted in considerable stiffening of the matrix simultaneous coculture and layered seeding of scaffolds with stromal cells followed by epithelial cells gave similar results with good initial urothelial attachment (followed by loss of cells later) and slow stromal cell penetration.

CONCLUSION

We describe a decellularized sterilized porcine UBM with acceptable mechanical properties that shows promise as a scaffold for producing an in vitro tissue-engineered bladder patch material for lower urinary tract reconstruction. Future work now needs to focus on the conditions for achieving secure epithelial attachment.

Treatment-resistant detrusor overactivity--underlying pharmacology and potential mechanisms

Bladder function during filling and micturition is regulated by peripheral and central nervous and hormonal control systems. Micturition occurs in response to afferent signals from the lower urinary tract, and distention of the bladder wall is the primary stimulus. In the animal and human bladder, efferent adrenergic, cholinergic and nonadrenergic, noncholinergic (NANC) neurotransmission has been demonstrated. The most important receptors for activation of contraction are muscarinic (M3) and purinergic receptors (P2X1), however, the contribution of these receptors to contraction may differ between species, and may be changed in bladder dysfunction associated with detrusor overactivity (DO) and/or the overactive bladder (OAB) syndrome, such as outflow obstruction, neurogenic bladders, idiopathic DO and diabetes. The NANC component of the nerve-induced response in such disorders may be responsible for up to 40-50% of the total bladder contraction. Whether this in vitro'atropine-resistance' corresponds to DO/OAB seen in patients not responding to antimuscarinic treatment is not known. Afferent signalling from the urothelium may be involved in both normal bladder function and in DO/OAB, but its role in antimuscarinic-refractory patients remains to be established. Several central nervous system (CNS) transmitters/transmitter systems, including gamma aminobutyric acid (GABA), opioid, serotonin, noradrenaline, dopamine or glutamatergic receptors and mechanisms are known to be involved in micturition control. The contribution of these receptors and mechanisms in DO/OAB resistant to treatment with antimuscarinics is not known, but drugs acting at these sites may offer future treatment possibilities.

Alterations to network of NO/cGMP-responsive interstitial cells induced by outlet obstruction in guinea-pig bladder

Interstitial cells (ICs) play a role in regulating normal bladder activity. This study explores the possibility that the sub-urothelial and muscle networks of NO/cGMP-responsive ICs are altered in animals with surgically induced outflow obstruction. In sham-operated animals, the urothelium comprised NO-stimulated cGMP-positive (cGMP(+)) umbrella cells, an intermediate layer and a basal layer that stained for nNOS. cGMP(+) sub-urothelial interstitial cells (su-ICs) were found below the urothelium. cGMP(+) cells were also associated with the outer muscle layers: on the serosal surface, on the surface of the muscle bundles and within the muscle bundles. Several differences were noted in tissues from obstructed animals: (1) the number of cGMP(+) umbrella cells and intensity of staining was reduced; (2) the intermediate layer of the urothelium consisted of multiple cell layers; (3) the su-IC layer was increased, with cells dispersed being throughout the lamina propria; (4) cGMP(+) cells were found within the inner muscle layer forming nodes between the muscle bundles; (5) the number of cells forming the muscle coat (serosa) was increased; (6) an extensive network of cGMP(+) cells penetrated the muscle bundles; (7) cGMP(+) cells surrounded the muscle bundles and nodes of ICs were apparent, these nodes being associated with nerve fibres; (8) nerves were found in the lamina propria but rarely associated with the urothelium. Thus, changes occur in the networks of ICs following bladder outflow obstruction. These changes must have functional consequences, some of which are discussed.

Mechanisms of Disease: the role of nerve growth factor in the pathophysiology of bladder disorders

The case is compelling for the involvement of nerve growth factor (NGF) in the pathogenesis of lower urinary tract disease, especially in conditions with altered neural function. Remodeling of the micturition pathways occurs following experimental bladder-outlet obstruction, denervation, spinal cord injury, cystitis, and diabetes mellitus. Clinically, NGF levels are elevated in the bladders of men with benign prostatic hyperplasia, women with interstitial cystitis and in patients with idiopathic overactive bladder. Blockade of NGF, using either an endogenous antibody or an antibody against the NGF receptor, prevents neural plasticity and bladder overactivity in experimental models of these conditions. The ability of NGF to trigger bladder overactivity might rely on altering the properties of sodium or potassium channels (or their expression) in bladder afferent fibers. Therapies based on altered NGF levels, or changes in channel properties in afferent nerves, represent an intriguing avenue of investigation for the management of detrusor overactivity or diabetic cystopathy.

The overactive bladder: review of current pharmacotherapy in adults. Part 1: pathophysiology and anticholinergic therapy

Overactive bladder is a syndrome characterised by urinary urgency, with or without urge incontinence, and usually with frequency and nocturia. It affects millions of people of all ages worldwide and causes significant morbidity, especially in terms of health-related quality of life. It poses a huge economic burden on health resources. Managing such patients involves a thorough history, physical examination and the use of pertinent investigations before the initiation of treatment. Therapy consists of lifestyle changes, bladder training, anticholinergics, second-line agents such as resiniferatoxin instillation or botulinum toxin injections into the bladder in refractory cases and, finally, in intractable cases, surgery. In the first part of this review of pharmacotherapy for the treatment of this condition, the focus is on the pathophysiological factors potentially involved in overactive bladder and covers the wide range of currently available first-line anticholinergic agents. Treatment algorithms are suggested on the basis of current literature.

Pathophysiology of overactive bladder

Overactive bladder (OAB) is a complex of symptoms frequently encountered in the primary care setting. Impediments to optimal management of OAB include inaccurate perceptions on the part of patients and primary care providers, e.g., that the symptoms of OAB represent a natural progression of aging and are beyond the scope of treatment or that diagnosis and treatment are specialist concerns. Complicating the physician's task is the reluctance of many patients to initiate discussion of their OAB symptoms and the fact that patients often develop disruptive coping strategies rather than seek medical treatment, possibly because of a belief that OAB is a normal part of aging rather than an actual medical condition. In most cases, OAB may be managed quite well by the primary care physician who has an understanding of the pathophysiology of OAB. This article reviews normal bladder function and then explores pathophysiologic changes that likely cause the symptoms of OAB.

Overactive bladder in the male patient: epidemiology, etiology, evaluation, and treatment

The urologist's approach to the diagnosis and treatment of lower urinary tract symptoms (LUTS) in male patients has changed significantly over the past decade. Advances in the basic science arena combined with a wealth of clinical data have pointed to the importance of bladder pathophysiology in the development of urinary symptoms. Historically, men with LUTS were diagnosed with "prostatism," an all-encompassing term that includes both voiding and storage symptoms that may or may not be related to prostatic obstruction. Parallel to the scientific advances in the field, the urologic lexicon began to evolve and has allowed us to more specifically describe, and therefore investigate and treat, different aspects of male LUTS. It is now well recognized that many men suffer from storage symptoms that may be more related to bladder dysfunction than to prostatic obstruction. It will be critical to integrate our knowledge of prostatic growth and obstruction, the bladder response to outlet obstruction, environmental and lifestyle factors, and age-related changes to fully understand the complex pathophysiology of male LUTS, specifically overactive bladder syndrome.

Quantification of bladder smooth muscle orientation in normal and spinal cord injured rats

Spinal cord injuries (SCI) often lead to severe bladder dysfunctions. Our previous studies have demonstrated that following SCI, rat bladder wall tissue became hypertrophied, significantly more compliant, and changed its mechanical behavior from orthotropic to isotropic. In order to elucidate the link between the tissue microstructure and mechanical properties of the wall, we have developed a novel semi-automated image analysis method to quantify smooth muscle bundle orientation and mass fraction in the bladder wall tissues from normal and 10 day-post-SCI rats. Results of the present study revealed that there were significant (p < 0.05) increases in smooth muscle area fractions as well as significantly (p < 0.001) fewer cell nuclei per muscle area in the SCI groups compared to the normal groups. Furthermore, while the normal rat bladders exhibited predominant smooth muscle orientation only in the longitudinal direction, the SCI rat bladders exhibited smooth muscles oriented in both the circumferential and longitudinal directions. These results provide first evidence that bladder smooth muscle cells exhibit hypertrophy rather than hyperplasia and developed a second, orthogonal orientation of smooth muscle bundles following SCI. The results of the present study corroborate our previous mechanical anisotropy data and provide the basis for development of structure-based constitutive models for urinary bladder wall tissue.

Pharmacology of the lower urinary tract: basis for current and future treatments of urinary incontinence

The lower urinary tract constitutes a functional unit controlled by a complex interplay between the central and peripheral nervous systems and local regulatory factors. In the adult, micturition is controlled by a spinobulbospinal reflex, which is under suprapontine control. Several central nervous system transmitters can modulate voiding, as well as, potentially, drugs affecting voiding; for example, noradrenaline, GABA, or dopamine receptors and mechanisms may be therapeutically useful. Peripherally, lower urinary tract function is dependent on the concerted action of the smooth and striated muscles of the urinary bladder, urethra, and periurethral region. Various neurotransmitters, including acetylcholine, noradrenaline, adenosine triphosphate, nitric oxide, and neuropeptides, have been implicated in this neural regulation. Muscarinic receptors mediate normal bladder contraction as well as at least the main part of contraction in the overactive bladder. Disorders of micturition can roughly be classified as disturbances of storage or disturbances of emptying. Failure to store urine may lead to various forms of incontinence, the main forms of which are urge and stress incontinence. The etiology and pathophysiology of these disorders remain incompletely known, which is reflected in the fact that current drug treatment includes a relatively small number of more or less well-documented alternatives. Antimuscarinics are the main-stay of pharmacological treatment of the overactive bladder syndrome, which is characterized by urgency, frequency, and urge incontinence. Accepted drug treatments of stress incontinence are currently scarce, but new alternatives are emerging. New targets for control of micturition are being defined, but further research is needed to advance the pharmacological treatment of micturition disorders.

Uropathic observations in mice expressing a constitutively active point mutation in the 5-HT3A receptor subunit

Mutant mice with a hypersensitive serotonin (5-HT)3A receptor were generated through targeted exon replacement. A valine to serine mutation (V13'S) in the channel-lining M2 domain of the 5-HT3A receptor subunit rendered the 5-HT3 receptor 70-fold more sensitive to serotonin and produced constitutive activity when combined with the 5-HT3B subunit. Mice homozygous for the mutant allele (5-HT3Avs/vs) had decreased levels of 5-HT3A mRNA. Measurements on sympathetic ganglion cells in these mice showed that whole-cell serotonin responses were reduced, and that the remaining 5-HT3 receptors were hypersensitive. Male 5-HT3Avs/vs mice died at 2-3 months of age, and heterozygous (5-HT3Avs/+) males and homozygous mutant females died at 4-6 months of age from an obstructive uropathy. Both male and female 5-HT3A mutant mice had urinary bladder mucosal and smooth muscle hyperplasia and hypertrophy, whereas male mutant mice had additional prostatic smooth muscle and urethral hyperplasia. 5-HT3A mutant mice had marked voiding dysfunction characterized by a loss of micturition contractions with overflow incontinence. Detrusor strips from 5-HT3Avs/vs mice failed to contract to neurogenic stimulation, despite overall normal responses to a cholinergic agonist, suggestive of altered neuronal signaling in mutant mouse bladders. Consistent with this hypothesis, decreased nerve fiber immunoreactivity was observed in the urinary bladders of 5-HT3Avs/vs compared with 5-HT3A wild-type (5-HT3A+/+) mice. These data suggest that persistent activation of the hypersensitive and constitutively active 5-HT3A receptor in vivo may lead to excitotoxic neuronal cell death and functional changes in the urinary bladder, resulting in bladder hyperdistension, urinary retention, and overflow incontinence.

Urinary bladder contraction and relaxation: physiology and pathophysiology

The detrusor smooth muscle is the main muscle component of the urinary bladder wall. Its ability to contract over a large length interval and to relax determines the bladder function during filling and micturition. These processes are regulated by several external nervous and hormonal control systems, and the detrusor contains multiple receptors and signaling pathways. Functional changes of the detrusor can be found in several clinically important conditions, e.g., lower urinary tract symptoms (LUTS) and bladder outlet obstruction. The aim of this review is to summarize and synthesize basic information and recent advances in the understanding of the properties of the detrusor smooth muscle, its contractile system, cellular signaling, membrane properties, and cellular receptors. Alterations in these systems in pathological conditions of the bladder wall are described, and some areas for future research are suggested.

Mitochondrial metabolism in the rat during bladder regeneration induced by small intestinal submucosa

OBJECTIVE

To assess mitochondrial metabolism of bladder tissue induced by small-intestinal submucosa (SIS), by comparing the mitochondrial enzyme metabolism in this tissue with that in normal bladder tissue and thus evaluate intracellular normality.

MATERIAL AND METHODS

In all, 70 rats were grouped into healthy controls (10), surgical controls with a simple bladder incision (15) and rats treated by partial cystectomy with replacement by the SIS graft (45). At 1, 3 and 6 months the rats were killed, the enzymes of mitochondrial respiratory chain complexes assayed, and the respiration of permeabilized bladder fibres assessed using polarographic analysis.

RESULTS

The enzyme activities of control and treated rats at 3 months were identical. The results from the polarographic analysis of respiration were also similar to that in normal tissue apart from a decrease in the number of mitochondria. Histologically, there was complete regeneration at 6 months.

CONCLUSION

After a phase of inflammation the bladder regenerates after a patch is placed. The new tissue has the same enzymatic and histological features as normal bladder tissue.

Storage and voiding symptoms: pathophysiologic aspects

Lower urinary tract symptoms (LUTS) can be categorized as storage, voiding, and postmicturition symptoms. Although often associated with benign prostatic hyperplasia (BPH), they may also occur in women. This observation, the beneficial effects of alpha-adrenoceptor (AR) antagonists in men with BPH and LUTS, and the frail correlation between LUTS, and prostatic enlargement and/or outflow obstruction have focused interest on the role of extraprostatic alpha-ARs in the pathogenesis of LUTS. It has been suggested that an upregulation of contraction-mediating alpha-ARs and a downregulation of relaxation-mediating beta-ARs can contribute to LUTS generation. However, recent investigations on human bladder tissue could not confirm such a change. Antimuscarinic agents are effective for treatment of the overactive bladder, which is characterized by urge, frequency, urge incontinence, and nocturia (ie, LUTS). This suggests that muscarinic receptors are involved in the pathogenesis of LUTS, and there is recent evidence implicating purinergic receptors. Structural changes in the bladder, such as smooth muscle hypertrophy and connective tissue infiltration, are associated with detrusor overactivity in about 50% to 66% of patients with BPH. However, it is unclear whether this is caused by bladder outlet obstruction because the symptoms may remain in up to 33% of the patients after surgical removal of the obstruction. When outflow obstruction is reversed in rats, there is a subset (20%) that continues to have overactive voiding, despite a reversal of the bladder hypertrophy, suggesting that changes within the central nervous system may be a contributing factor. LUTS can be caused by many, often overlapping, pathophysiologic mechanisms, which may contribute to individual variation in response to treatment.

Muscarinic receptors: What we know

An understanding of muscarinic receptors is tantamount to an understanding of overactive bladder. The M(3) muscarinic receptor subtype is responsible for detrusor smooth muscle contraction and it exerts an exocrine function in the salivary glands. Alterations in the receptor's response to acetylcholine as a result of injury may lead to hypersensitivity and overactivity. The M(2) receptor subtype, which is mainly responsible for cardiac function, is the muscarinic receptor of highest proportion in the detrusor. M(2) also may play a role in detrusor contraction in injury and pathologic states. Muscarinic antagonists are the mainstay of pharmacotherapy for overactive bladder, but those that are available are not tissue specific. Growing knowledge of the nuances of receptor-ligand behavior and interaction between muscarinic receptors subtypes may provide novel targets for future drug development, improve efficacy, and reduce bothersome side effects.

Bladder overactivity in mice after 1 week of outlet obstruction. Mainly afferent dysfunction?

PURPOSE

Partial bladder outlet obstruction (BOO) is an established way to create bladder overactivity in animals. However, the micturition pattern achieved can vary considerably. We investigated the correlation between different micturition patterns, post-void residual urine, bladder capacity, bladder weight and in vitro contractility in a conscious mouse model of BOO.

MATERIALS AND METHODS

Female MNRI mice with moderate (urethral) outlet obstruction were used. After 7 days of BOO cystometry without anesthesia was performed with the animal in a metabolic cage. Results were compared with those in unoperated controls and sham operated animals. In vitro contractility studies were performed.

RESULTS

The majority of obstructed animals had an overactive voiding pattern with increased nonvoiding detrusor activity and without increased bladder weight. The remaining obstructed animals had significantly increased bladder weight and normal micturition volume but increased threshold pressure, bladder capacity and post-void residual urine. Subtle in vitro differences were found among the groups.

CONCLUSIONS

The urodynamic characteristics of BOO mice correlate with bladder weight. However, detrusor overactivity in obstructed mice may develop without an increase in bladder weight and with only subtle changes in smooth muscle function, as investigated in vitro. This observation suggests that major disturbances caused by BOO may lie in the afferent arm of the signaling pathway.

Innervation of the detrusor muscle bundle in neurogenic detrusor overactivity

OBJECTIVE

To evaluate the peripheral anatomical distribution of innervation within muscle bundles of the detrusor and the changes arising in neurogenic detrusor overactivity (DO).

PATIENTS AND METHODS

Full-thickness samples from the bladder dome of three cadaveric transplant organ donors and four people with neurogenic DO caused by spinal cord injury were compared. Systematic serial cryostat sections were stained using Masson trichrome and elastin techniques, and vimentin immunohistochemistry. A coherent image stack was generated for three-dimensional image reconstructions, which were displayed using mixed rendering (i.e. differing graphics for separate tissue components) to show peri- and intra-bundle innervation against the muscle fascicle framework.

RESULTS

Control specimens had a dense nerve supply. Muscle bundle innervation was derived by dichotomous branching from peri-bundle nerve trunks in the inter-bundle connective tissue. Transverse interfascicular branches entered bundles perpendicular to the long axis at the midpoint of the bundle. They gave rise to axial interfascicular branches, which distributed to the pre-terminal and terminal nerve fibres. All samples from patients with neurogenic DO had patchy denervation. The primary deficit was predominantly at the level of the terminal axial innervation and was cross-sectionally consistent along the longitudinal axis of the muscle bundle.

CONCLUSION

Patchy denervation may reflect a deficit at the level of the peripheral ganglia. Any contraction in the areas of denervation either occurs out of co-ordination with the rest of the bladder, or is co-ordinated by means of non-neural structures. The observation of fine muscle strands running between fascicles, and connective tissue anchoring structures, represent two hypothetical mechanisms by which such co-ordination might be effected.

A prospective evaluation of detrusor ultrastructural changes in bladder outlet obstruction

OBJECTIVES

To characterize the ultrastructure of detrusor smooth muscle from the bladders of symptomatic men with bladder outlet obstruction (BOO) caused by benign prostatic enlargement (BPE) and compare this with a matched control group; to determine how detrusor morphology relates to urodynamic findings and to develop a better understanding of the natural development of bladder dysfunction related to BOO.

PATIENTS AND METHODS

Twelve men (mean age 66 years, range 52-77) with urodynamically confirmed BOO caused by BPE and 12 age-matched asymptomatic normally voiding controls (mean age 67.8 years, undergoing cystoscopy for other conditions) had detrusor biopsies taken endoscopically. The biopsies were processed for electron microscopy using standard methods. The specimens were randomized and examined at medium power (x 4000) by an examiner unaware of the urodynamic findings. Any ultrastructural patterns identified subjectively were noted.

RESULTS

In the BOO group eight of the 12 men had a myohypertrophic pattern, half of which were associated with a degenerative pattern of hypocontractility. Of the remaining four patients, two had the degenerative pattern alone and two were normal. The six men whose biopsies had a degenerative pattern had consistent postvoid residual volumes of > 150 mL; the remainder all had volumes of < 150 mL. There were no ultrastructural abnormalities in the control patients.

CONCLUSIONS

There are interesting qualitative ultrastructural changes in the obstructed detrusor, but they are not consistent enough to provide a reliable diagnostic tool. However, there may be an important relationship between the degenerative pattern and postvoid residual volume in BOO.

Antimuscarinics and the overactive detrusor--which is the main mechanism of action?

Contraction of the bladder, voluntary or involuntary, involves stimulation of the muscarinic receptors on the detrusor by acetylcholine, released from activated cholinergic nerves. Antimuscarinics are the drugs of choice for treatment of detrusor overactivity and the overactive bladder (OAB) syndrome. However, antimuscarinics at clinically recommended doses have little effect on voiding contractions, and may act mainly during the bladder storage phase, during which there is normally no parasympathetic outflow from the spinal cord. Supporting this, antimuscarinics have been shown to reduce bladder tone during storage, and to increase cystometric bladder capacity. A basal release of acetylcholine from non-neuronal (urothelial) as well as neuronal sources has been demonstrated in isolated human detrusor muscle. It is suggested that this release, which is increased by stretching the muscle and in the aging bladder, contributes to detrusor overactivity and OAB by eventually increasing bladder afferent activity during storage.

Mechanical stretch regulates cell survival in human bladder smooth muscle cells in vitro

Our understanding of the pathophysiology of the overactive bladder is poor. It has been proposed that localized contractions result in the abnormal stretching of bladder smooth muscle. We hypothesize that stretch regulates the cellular processes that determine tissue size. The purpose of this study was to investigate the effect of stretch on apoptosis, proliferation, cell hypertrophy, and growth factor production in human bladder smooth muscle cells in vitro. Normal human detrusor muscle was obtained from patients undergoing radical cystectomy for invasive bladder cancer, and primary cultures were established. Cells were mechanically stretched on flexible plates at a range of pressures and times. Apoptosis was assessed by propidium iodide incorporation and flow cytometry. Radiolabeled thymidine and amino acid incorporation were used to assess proliferation and cell hypertrophy. ELISA and RT-PCR were used to assess growth factor production. Mechanical stretch inhibits apoptosis in a time- and dose-dependent manner and was associated with increases in the antiapoptotic proteins heat shock protein-70 and cIAP-1. Stretch also increases smooth muscle cell proliferation and hypertrophy, but hypertrophy is the more dominant response. These changes were associated with increases in IGF-1 and basic FGF and a decrease in transforming growth factor-beta1. Mechanical stretch regulates apoptosis, proliferation, and cell hypertrophy in human bladder smooth muscle cells.

The effect of ovariectomy and long-term estrogen replacement on bladder structure and function in the rat

PURPOSE The use of estrogen replacement therapy for treating postmenopausal urinary incontinence is a controversial topic. We examined the behavioral, cystometric and histological changes that occur with long-term estrogen depletion and supplementation in rat bladders to determine the role of menopause in lower urinary tract dysfunction. MATERIALS AND METHODS A total of 40 female Sprague-Dawley rats were placed into 1 of 3 groups, including bilateral ovariectomy, bilateral ovariectomy plus estrogen replacement and control. The estrogen replaced group received a 0.25 mg. 16-week sustained release pellet (Innovative Research of America, Sanasota, Florida) placed subcutaneously. After surgery voiding frequency and volume were measured in 24-hour periods by placing animals in metabolic cages. After 16 weeks the rats underwent catheterization and continuous cystometry. The bladder was then removed and stained with Gomori trichrome. The collagen-to-smooth muscle density ratio was calculated for each specimen using current imaging software. RESULTS There was no significant difference in voiding patterns in the 3 groups, as measured by volume and voiding frequency. Cystometric data showed a trend toward higher voiding pressure, threshold pressure, baseline pressure and mean inter-voiding pressure in the ovariectomy group compared with the estrogen and control groups, although there was no statistical significance. Histological studies showed a higher mean collagen-to-smooth muscle ratio plus or minus standard deviation in the ovariectomy group (0.807 +/- 0.204) than in the ovariectomy plus estrogen replacement (0.709 +/- 0.118) and control (0.700 +/- 0.129) groups (p <0.05). Furthermore, when histological and cystometric data were compared for individual samples, we found a direct correlation of mean inter-voiding pressure (a measure of bladder instability) with the collagen-to-smooth muscle ratio (p <0.05). CONCLUSIONS Long-term estrogen replacement is beneficial for treating postmenopausal urinary incontinence.

The cellular basis of contraction in human detrusor smooth muscle from patients with stable and unstable bladders

Studying the cellular physiology of human detrusor muscle obtained from patients with normally functioning bladders and comparing it with that of detrusor muscle from patients with unstable bladders may help identify potential targets for drug therapy in patients with abnormal bladder function. Considerable advances have been made in the understanding of the cellular processes that result in contraction and relaxation of detrusor smooth muscle, particularly in the role and modulation of calcium. Several changes in these cellular mechanisms that impair normal function have been observed in detrusor muscle from patients with unstable bladders. Whether these changes represent primary causes of bladder dysfunction or whether they are secondary to bladder dysfunction remains to be determined. Nevertheless, the identification of specific cellular lesions in bladder dysfunction presents a novel approach to identification of drug targets and potential treatment modalities.

Model of peripheral autonomous modules and a myovesical plexus in normal and overactive bladder function

Normal bladder function is controlled by the central nervous system (CNS) and any peripheral contribution to bladder control is believed to be small. Nevertheless, anatomically and functionally, such a contribution might exist. Taking account of this evidence, we propose that the detrusor muscle is arranged into modules, which are circumscribed areas of muscle active during the filling phase of the micturition cycle. These modules might be controlled by a peripheral myovesical plexus, consisting of intramural ganglia and interstitial cells. Detrusor overactivity is the occurrence of abnormal increases in pressure during bladder filling, which the patient cannot inhibit. This disorder is thought to be a consequence of abnormal expression of the micturition reflex or changes in the properties of the smooth muscle. We propose that detrusor overactivity results from exaggerated symptomatic expression of peripheral autonomous activity, resulting from a shift in the balance of excitation and inhibition in smooth muscle modules. These structures responsible for origin and spread of peripheral autonomous activity could be targeted to help develop new therapeutic strategies.