Alternative use of botulinum toxin in urology

Botulinum toxin A is used in the treatment of lower urinary tract symptoms due to detrusor sphincter dysynergia and detrusor hyper-reflexia (neurogenic detrusor deficiency). The toxin acts by producing paralysis of muscle tissue and has been shown to be safe and effective in the treatment of conditions caused by increased muscle tonicity and spasticity. Here the literature is reviewed chronologically, the established and emerging indications for the urological use of botulinum toxin evaluated and future applications are also considered.     

The role of botulinum toxin in neurourology

Botulinum toxin is a presynaptic neuromuscular blocking agent that induces a selective and reversible muscle weakness of up to several months when injected intramuscularly in minute quantities. Different medical disciplines have applied the toxin to treat mainly muscular hypercontraction. For neurourologically impaired patients, the reported successful treatment of neurogenic detrusor overactivity and detrusor sphincter dyssynergia with botulinum-A toxin is a promising alternative option to conservative medication or surgery. This review of the literature presents current indications, techniques for and results of the use of botulinum toxin in neurourologically impaired patients and aims to give an insight into this new therapeutic option.     

Botulinum toxin A for the Treatment of Overactive Bladder

The standard treatment for overactive bladder starts with patient education and behavior therapies, followed by antimuscarinic agents. For patients with urgency urinary incontinence refractory to antimuscarinic therapy, currently both American Urological Association (AUA) and European Association of Urology (EAU) guidelines suggested that intravesical injection of botulinum toxin A should be offered. The mechanism of botulinum toxin A includes inhibition of vesicular release of neurotransmitters and the axonal expression of capsaicin and purinergic receptors in the suburothelium, as well as attenuation of central sensitization. Multiple randomized, placebo-controlled trials demonstrated that botulinum toxin A to be an effective treatment for patients with refractory idiopathic or neurogenic detrusor overactivity. The urinary incontinence episodes, maximum cystometric capacity, and maximum detrusor pressure were improved greater by botulinum toxin A compared to placebo. The adverse effects of botulinum toxin A, such as urinary retention and urinary tract infection, were primarily localized to the lower urinary tract. Therefore, botulinum toxin A offers an effective treatment option for patients with refractory overactive bladder.     

Botulinum toxin for the management of bladder dysfunction

This review highlights a recent innovation in the medical treatment of detrusor overactivity (DO). Anticholinergics are usually the gold standard to treat bladder overactivity. Adverse effects and lack of efficacy are the two main causes for considering alternative treatments. Until recently, invasive surgery (mainly bladder augmentation) was the only available treatment option for patients with intractable DO. This article considers botulinum toxin type A (BTX-A) injection as an alternative treatment to surgery in patients with DO who do not respond to anticholinergic therapy. To identify papers for inclusion in this review, we searched PubMed with the keywords 'botulinum toxin', 'overactive bladder', 'urinary incontinence' and 'neurogenic bladder' for the years 2000-5. Review articles were not included. Abstracts were cited only if they contained important new information. Experimental animal studies and articles or book chapters related to the use of botulinum toxin for other indications (such as achalasia and cervical dystonia) were analysed with regard to the mechanisms of action of botulinum toxin.From this review, it appears that BTX-A injection into the detrusor muscle is a very effective method for treating urinary incontinence secondary to neurogenic detrusor overactivity (NDO), as well as urinary incontinence due to idiopathic overactive bladder (IDO). In both conditions, the duration of effect seems to be at least 6 months. Overall success rates seem to be similar in both patient populations. For NDO, only one evidence-based medicine level 1 study is available, whereas for IDO, only evidence-based medicine level 3 or 4 studies have been published. Particularly in this latter indication, injection technique and outcome parameters vary from study to study and need to be standardised. Without randomised controlled studies aimed at comparing different techniques and dosages, it remains difficult to decide what technique is optimal for treating patients with IDO who are not willing to perform clean intermittent self-catheterisation (CISC). Therefore, studies that compare different dosages and techniques with the risk of needing CISC in regard to the duration of the effect are mandatory. As more studies of repeated injections have been published, it appears that, at least at medium follow-up, the toxin remains as effective as after the first injection, and there is no evidence of change in bladder compliance or detrusor fibrosis. However, long-term observational studies are necessary to assess these last points. Finally, the commonly reported dose appears to be well tolerated, since few adverse effects have been reported.     

The action of palytoxin on the isolated detrusor muscle of the rat.

1. The effects of a coelenterate toxin, palytoxin (PTX) have been studied in the isolated detrusor muscle. of the rat. 2. PTX (1-100 nM) initiated concentration-dependent contractions of the detrusor; the contraction led to an irreversible tachyphylaxis. Muscle desensitized to PTX continued to respond to acetylcholine (ACh) and excess K+ but the contractions were reduced compared to pre-PTX contractions. 3. Contractions evoked by PTX were not affected by the presence of atropine (10 microM), indomethacin (10 microM) or tetrodotoxin (0.5 microM) but were greatly reduced by nifedipine (3 microM) and by the absence of K+. PTX could not evoke contractions in the absence of Ca2+ or in tissues depolarized by exposure to excess K+. 4. PTX abolished the neurogenic contractile responses to electrical field stimulation (EFS). 5. Combined treatment with atropine (10 microM) plus nifedipine (3 microM) abolished contractile responses to EFS and greatly reduced the contractile response to PTX. 6. The contractile response to PTX (100 nM) was reduced following exposure of the muscle to alpha, beta-methylene ATP. 7. Exposure to PTX (100 nM) for 1-3 h reduced both the ACh content of the detrusor (by more than 80%), and the immunoreactivity of neuropeptide Y-containing nerve fibres compared to control. 8. It is concluded that the primary effect of PTX is to promote the release of endogenous motor transmitters, leading to their eventual depletion.     

Inhibition of isolated rat and human detrusor muscle contraction by disopyramide

1. The aim of this study was to investigate the effect of in vitro and in vivo disopyramide treatment on human and rat isolated detrusor muscle contractile response. Muscle strips were suspended in an organ bath chamber containing Kreb's solution at 37 degrees C aerated with 95% oxygen and 5% carbon dioxide. 2. Disopyramide antagonized significantly the contractile response of isolated human detrusor muscle to carbachol stimulation, shifting the concentration-response curve to the right in a parallel manner. The pA2 for competitive inhibition was estimated to be 6.4 with a slope of 0.64 for disopyramide. 3. Rat detrusor muscle contractile response to electrical field stimulation (EFS) was inhibited by 28% (P < 0.01) after in vitro administration of disopyramide (7.5 x 10(-6) M). Disopyramide had no effect on the atropine-resistant component of the response to EFS or on spontaneous contractions of isolated rat detrusor muscle strips. The concentration-response curve to carbachol was competitively antagonized by disopyramide with a pA2 of 6.3 and a Schild curve a slope of 0.85. 4. Disopyramide (7.5 x 10(-6) M) had no effect on rat detrusor contractile response to low concentrations of KCl but at high concentrations contraction was reduced significantly by 16% (P < 0.01). 5. In vivo treatment of rats with disopyramide for 8 days or with a single dose had a significant inhibitory effect on the contractile response of detrusor muscle strips. 6. In conclusion, disopyramide had a significant anticholinergic effect on isolated human and rat detrusor muscle contraction.     

针灸治疗BPH致膀胱逼尿肌收缩无力TURP术后的临床观察

目的观察针灸治疗良性前列腺增生致膀胱逼尿肌无力患者经尿道前列腺电切术后效果。方法选择因良性前列腺增生、膀胱过度充盈致逼尿肌损伤,引起膀胱逼尿肌收缩无力并行经尿道前列腺电切术38例患者,术后采用电针刺激关元、中极、肾俞、次髎、三阴交、足三里穴,观察疗效。结果治疗4个疗程后,35例TURP术后留置膀胱造瘘管（1～8）周后全部拔除,排尿通畅。3例膀胱逼尿肌收缩功能几乎无任何改善。长期留置膀胱造瘘治疗。结论针灸治疗良性前列腺增生致膀胱逼尿肌无力经尿道前列腺电切术后疗效明确,可以减少膀胱造瘘率,提高患者的生活质量。     

Tramadol inhibits the contractility of isolated caprine detrusor muscle

1 The atypical opioid analgesic tramadol has been shown to provide beneficial clinical and urodynamic effects in patients with detrusor overactivity. The effect of tramadol on isolated detrusor muscle has not been studied. This study investigated the ability of tramadol to inhibit acetylcholine (ACh)‐induced contractility of the isolated caprine (goat) detrusor muscle. The effect of three concentrations (30, 100 and 300 μm ) of tramadol on 10 caprine detrusor strips contracted by the addition of 100, 200 or 400 μm ACh was studied. The sensitivity of tramadol‐induced inhibition of ACh responses to treatment with the β‐adrenoceptor antagonist propranolol (1 μm ) and the opioid receptor antagonist naloxone (100 μμ ) was also studied. 2 Tramadol caused a concentration‐dependent inhibition of ACh‐induced detrusor contraction that was reversed by raising the concentration of ACh. Propranolol, but not naloxone, reversed the tramadol‐induced inhibition of contractions to ACh in the detrusor. 3 These results suggest that tramadol inhibits ACh‐induced contractility of the isolated detrusor. They also suggest that tramadol does so by an indirect anticholinergic mechanism involving the stimulation of β‐adrenoceptors. Tramadol may be useful in managing clinical conditions requiring relaxation of the detrusor muscle. Although the concentrations of tramadol needed to relax the detrusor were relatively high, these could be clinically attained via intravesical administration.     

Afferent mechanism in the urinary tract

Much of the current research on lower urinary tract dysfunction is focused on afferent mechanisms. The main goals are to define and modulate the signaling pathways by which afferent information is generated and conveyed to the central nervous system. Alterations in bladder afferent mechanisms are a potential source of voiding dysfunction and an emerging source of drug targets. Even some established drug therapies such as muscarinic receptor antagonists, as well as emerging therapies such as botulinum toxin type-A, may act partly through afferent mechanisms. This review presents up-to-date findings on the localization of afferent fiber types within the bladder wall, afferent receptors and transmitters, and how these may communicate with the urothelium, interstitial cells, and detrusor smooth muscle to regulate micturition in normal and pathological bladders. Peripheral and central mechanisms of afferent sensitization and myogenic mechanisms that lead to detrusor overactivity, overactive bladder symptoms, and urgency sensations are also covered as well as new therapeutic approaches and new and established methods of measuring afferent activity.     

The overactive bladder: review of current pharmacotherapy in adults. Part 2: treatment options in cases refractory to anticholinergics

In the first part of this review the potential pathophysiological factors involved in the overactive bladder were outlined, and the wide range of first-line anticholinergic pharmacotherapies available for such patients were reviewed. The second part will focus on the intravesical instillation of resiniferatoxin and injections of botulinum toxin into the bladder to treat overactive bladder and detrusor overactivity. Resiniferatoxin has been shown to increase bladder capacity and improve incontinence in patients with neurogenic and non-neurogenic detrusor overactivity. Botulinum toxin has successfully been used to treat neurogenic and idiopathic detrusor overactivity, with improvements observed in bladder capacity, decreases in detrusor pressures on filling and voiding, and increased volumes at first contraction. Further validation is required for both treatments, in the form of large randomised controlled trials, before their use can be considered routine, with particular focus on dosing required.     

Inhibitory effect of nicorandil on the contraction of isolated human urinary bladder detrusor muscle

This study was performed to determine whether the antianginal drug nicorandil relaxes isolated human detrusor muscle. Ten strips of detrusor muscle obtained from 10 pediatric patients who underwent surgery on the urinary bladder were contracted with 80 mM potassium chloride (KCl) before and after incubation with four concentrations of nicorandil (100, 200, 400 and 800 microM). The percent inhibition by nicorandil of the height and area under the curve (AUC) of KCl-induced contractions of the detrusor strips was calculated. The effect of glibenclamide (10 microM) on nicorandil (800 microM)-induced inhibition of KCl-induced detrusor contractions was also studied. Nicorandil caused a concentration-dependent inhibition of KClinduced contractions of the detrusor strips. The percent inhibition of the height of KCl-induced contractions of the detrusor by nicorandil was significant at concentrations of 200, 400 and 800 microM. The percent inhibition of the AUC for KCl-induced detrusor contractions was significant at all four concentrations of nicorandil used. Glibenclamide reversed the inhibitory effect of 800 microM nicorandil on KCl-induced detrusor contractions. These results suggest that nicorandil inhibits KCl-induced contractions of isolated human detrusor muscle and may therefore be useful in clinical conditions requiring detrusor muscle relaxation.     

Inhibitory effect of anticholinergics on the contraction of isolated caprine urinary bladder detrusor muscle

1. This study investigated whether four anticholinergics which are not clinically used for relaxing the urinary bladder detrusor muscle inhibit the contraction of isolated caprine (goat) detrusor muscle: cyclopentolate (100 nm ), homatropine (5 μm ), ipratropium (500 nm ) and valethamate (1 μm ). 2. The effects of these anticholinergics were compared with tolterodine (3 μm ), an anticholinergic clinically used for relaxing the detrusor muscle. The inhibitory effect of each of these five anticholinergics was studied on six strips of caprine detrusor muscle made to contract with 100 μm acetylcholine (ACh) by determining the percent inhibition of height of contraction and the area under the contractile curve (AUC). 3. It was found that all five anticholinergics inhibited the ACh‐induced contraction of the caprine detrusor and that this inhibition was reversed by raising the concentration of ACh. Hence, these four anticholinergics, like tolterodine, may be useful in managing clinical conditions that require relaxation of the detrusor muscle.     

Inhibition of LIM kinase reduces contraction and proliferation in bladder smooth muscle

Overactive bladder (OAB) is the most bothersome symptom in lower urinary tract symptoms (LUTS). Current pharmacologic treatment aims to inhibit detrusor contraction; however, shows unsatisfied efficacy and high discontinuation rate. LIM kinases (LIMKs) promote smooth muscle contraction in the prostate; however, their function in the bladder smooth muscle remains unclear. Here, we studied effects of the LIMK inhibitors on bladder smooth muscle contraction and proliferation both in vitro and in vivo experiments. Bladder expressions of LIMKs are elevated in OAB rat detrusor tissues. Two LIMK inhibitors, SR7826 and LIMKi3, inhibit contraction of human detrusor strip, and cause actin filament breakdown, as well as cell proliferation reduction in cultured human bladder smooth muscle cells (HBSMCs), paralleled by reduced cofilin phosphorylation. Silencing of LIMK1 and LIMK2 in HBSMCs resulted in breakdown of actin filaments and decreased cell proliferation. Treatment with SR7826 or LIMKi3 decreased micturition frequency and bladder detrusor hypertrophy in rats with bladder outlet obstruction. Our study suggests that LIMKs may promote contraction and proliferation in the bladder smooth muscle, which could be inhibited by small molecule LIMK inhibitors. LIMK inhibitors could be a potential therapeutic strategy for OAB- related LUTS.KEY WORDS: LIMK, Cofilin phosphorylation, Overactive bladder (OAB), Lower urinary tract symptoms (LUTS), Bladder smooth muscle contraction     

Bladder instillation of Escherichia coli lipopolysaccharide alters the muscle contractions in rat urinary bladder via a protein kinase C-related pathway

Uropathogenic Escherichia coli is a common cause of urinary tract infection. We determined the effects of intravesical instillation of E. coli lipopolysaccharide (LPS, endotoxin) on muscle contractions, protein kinase C (PKC) translocation, and inducible nitric oxide synthase (iNOS) expression in rat urinary bladder. The contractions of the isolated rat detrusor muscle evoked by electrical field stimulations were measured short-term (1 h) or long-term (24 h) after intravesical instillation of LPS. One hour after LPS intravesical instillation, bladder PKC-alpha translocation from cytosolic fraction to membrane fraction and endothelial (e)NOS protein was elevated, and detrusor muscle contractions were significantly increased. PKC inhibitors chelerythrine and Ro32-0432 inhibited this LPS-enhanced contractile response. Application of PKC activator beta-phorbol-12,13-dibutyrate enhanced the muscle contractions. Three hours after intravesical instillation of LPS, iNOS mRNA was detected in the bladder. Immunoblotting study also demonstrated that the induction of iNOS proteins is detected in bladder in which LPS was instilled. 24 h after intravesical instillation of LPS, PKC-alpha translocation was impaired in the bladder; LPS did not affect PKC-delta translocation. Muscle contractions were also decreased 24 h after LPS intravesical instillation. Aminoguanidine, a selective iNOS inhibitor, blocked the decrease in PKC-alpha translocation and detrusor contractions induced by LPS. These results indicate that there are different mechanisms involved in the alteration of urinary bladder contractions after short-term and long-term treatment of LPS; an iNOS-regulated PKC signaling may participate in causing the inhibition of muscle contractions in urinary bladder induced by long-term LPS treatment.     

The effect of pregnancy and the oestrus cycle on purinergic and cholinergic responses of the rat urinary bladder

The urinary bladder undergoes plastic changes during physiological alterations such as pregnancy. This study has shown that bladders from pregnant rats weighed three times more than bladders from virgin rats. Each milligram of detrusor muscle from pregnant rats contracted more strongly to nerve stimulation (150% greater) and agonists (50% greater or more) compared to detrusor from virgin rats at any stage during the oestrus cycle. The purinergic component of nerve-mediated responses altered during the oestrus cycle, being greatest during oestrus (oestrogen and progesterone fall rapidly) and dioestrus (low oestrogen and progesterone), smaller during pregnancy and even smaller during pro-oestrus (high oestrogen and progesterone); in contrast the cholinergic component remained relatively unchanged. In conclusion, during pregnancy the detrusor muscle generates larger contractions compared to virgin detrusor muscle, probably due to hormonal influences on smooth muscle contraction mechanisms. As agonist responses were unchanged during the oestrus cycle, changes in the purinergic component of nerve stimulation was not due to altered P2 receptor expression but possibly to an increase in ATP release or a reduction in breakdown. The hormonal effect may have implications for the treatment of bladder disorders due to alterations in hormones, such as stress incontinence in post-menopausal women.     

合并急性尿潴留的良性前列腺增生逼尿肌功能评估及术后疗效预测

目的评估幌并急性尿潴留(AUR)的良性前列腺增生(BPH)患者逼尿肌功能,预测术后疗效。方法对23例合并AUR的BPH患者术前后行尿动力学检查,评估逼尿肌功能(包括逼尿肌紊定性、顺应性、收缩功能),在治疗成功组与失败组之间进行比较。结果23例患者中,16例(70%)发生逼尿肌无抑制性收缩(DI),幅度5~168 cm H2O,平均(98±33)cm H2O(1cm H2O=0.098 kPa);20例(87%)可见有逼尿肌随意收缩;所有患者均明确诊断膀胱出口梗阻(BOO);4例(17%)患者术后不能排尿,需要留置导尿。手术前后患者年龄、DI的发生率、DI幅度、膀胱顺应性及测压容量、逼尿肌收缩力强弱在治疗成功组与失败组之间的差异具有统计学意义(P<0.05)。结论合并AUR的BPH患者留置尿管10 d后行尿动力学检查,可以预测术后疗效。术前尿动力学检查DI幅度越大,逼尿肌收缩力越强,术后疗效越好;术前膀胱顺应性及测压容量异常增高、无DI出现者术后疗效差。     

Assessment of muscarinic receptor subtypes in human and rat lower urinary tract by tissue segment binding assay

Muscarinic receptors in the human and rat lower urinary tract (urinary bladder detrusor muscle and mucosa, and prostate) were identified by intact tissue segment binding assays with two radioligands, and the effects of prolonged receptor activation in vitro on muscarinic receptors were examined. Hydrophilic [(3)H]-NMS and hydrophobic [(3)H]-QNB bound to the detrusor muscle segments with the same density, suggesting that the muscarinic receptors were localized at the plasma membrane. While the density of muscarinic receptor was higher in detrusor muscle than in the bladder mucosa and prostate, there was no species-specific difference either in density or in subtype distribution (M(1), M(2), and M(3) subtypes in detrusor; M(2) and M(3) subtypes in bladder mucosa; and M(1) and M(2) subtypes in prostate). Incubation of detrusor strips with carbachol decreased [(3)H]-NMS binding sites within 20 min, followed by a reduction of [(3)H]-QNB binding sites after a 60-min lag phase. The loss of the binding sites over 3 h after carbachol treatment was the same (approximately 40%) for both radioligands. The present intact tissue segment binding assay reveals tissue-specific and plasma membrane distribution of distinct muscarinic receptor subtypes and their dynamic changes (internalization and down-regulation) in lower urinary tract of humans and rats.     

Effects of cernitin pollen extract (CN-009) on the isolated bladder smooth muscles and the intravesical pressure

Cernitin pollen extract (CN-009), extract from several pollen species, has been used for urinary dysfunction. As its mode of action has not been clarified, we investigated the action of CN-009 on the isolated bladder smooth muscles of rats, guinea pigs and cats and the intravesical pressure in female rats. CN-009 contracted isolated detrusor muscles of rats, guinea pigs and cats in a concentration-dependent manner. In the guinea pig detrusor muscle, the contractile effect of CN-009 was depressed by atropine, diphenhydramine and increased by cimetidine. In the rat detrusor muscle, the CN-009-induced contraction was depressed by atropine. In adult rats (11-23 weeks old) and aged rats (2 years old), CN-009 showed a dose-dependent increase of intravesical pressure to the same extent in spite of the fact that the aged rats had a lower responsiveness to acetylcholine. In adult rats, the CN-009-induced increase of intravesical pressure was reduced completely by atropine and partly reduced by phentolamine and guanethidine. Three weeks consecutive oral administration of CN-009 tended to increase the basal intravesical pressure and tended to elevate the isoproterenol-induced decrease and serotonin-induced increase in the intravesical pressure. These results suggest that CN-009 contracts the detrusor muscle, a process that is mainly mediated by muscarinic receptor activation. The contraction induced by CN-009 of detrusor muscle causes the increase of intravesical pressure.     

Doxazosin effects on cholinergic and adrenergic responses in rat isolated detrusor smooth muscle preparations from obstructed bladder

We investigated the effect of doxazosin on cholinergic and adrenergic agonists responses in detrusor smooth muscle preparations from sham-operated and 2-week partially obstructed rat bladders. Male Wistar albino rats, 200-250 g, were randomly allocated to 4 experimental groups consisting of 12 animals each: sham-operated bladder, sham-operated bladder treated with doxazosin, partially obstructed bladder, and partially obstructed bladder treated with doxazosin. Partial outlet obstruction of the rat was surgically induced. The response to carbachol (10(-7)-10(-4) M), isoproterenol (10(-6)-10(-3) M), and 80 mM KCl were recorded. Carbachol caused concentration-dependent contractile responses in the detrusor smooth muscles from sham-operated and partially obstructed bladder. Isoproterenol produced concentration-dependent relaxation responses in the detrusor strips from all groups. Dose-response curves for carbachol and isoproterenol showed a shift to the left in rat detrusor smooth muscles from partially obstructed bladder when compared with the results obtained in detrusor muscles from sham-operated bladder. These responses were reversed to normal by doxazosin treatment in rat detrusor smooth muscles from partially obstructed bladder. KCl produced contractile responses in rat detrusor smooth muscles from all groups. The contractile responses to KCl were not significantly changed in all groups. We have shown that carbachol and isoproterenol responses were shifted to the left in rat detrusor smooth muscles from partially obstructed bladder and these responses were reversed by doxazosin treatment.     

Purinergic P2X3 heteroreceptors enhance parasympathetic motor drive in isolated porcine detrusor, a reliable model for development of P2X selective blockers for detrusor hyperactivity

Various forms of low urinary tract symptoms (LUTS) seem dependant upon dysregulation of the purinergic pathway which produces sensory- or motor-activated incontinence. A body of evidence in human urinary bladders supports a link between up-regulation of purinergic activity and the pathogenesis of detrusor instability. This study investigated the potential role of adenosine 5'-triphosphate (ATP) in the control of detrusor motor drive in a model of porcine urinary bladder. The involvement of ATP on excitatory activity was assessed by measuring neurally-evoked [(3)H]-acetylcholine (ACh) release and smooth muscle contraction in detrusor strips. Epithelium-deprived preparations were used to minimize the influence of non-neural sources of ACh and ATP on parasympathetic neurotransmission. ACh release and smooth muscle contractility were not significantly affected by neural ATP in normal detrusor, but markedly enhanced when ATP hydrolysis was reduced by ectoATPase inhibitors, as well as by α,β-methylene-ATP (ABMA), agonist resistant to ecto-enzymes degradation. Prejunctional P2X receptors located on cholinergic nerves are involved in such potentiating effect. These purinergic heteroreceptors were characterized as P2X(3) subunits by means of the putative antagonists: NF449 (P2X(1,3) selective), NF023 (P2X(1,3) selective), PPNDS (P2X(1) selective) and A-317491 (P2X(3) selective). In porcine detrusor, P2X(3) receptors are functionally expressed at neural site facilitating neurogenic ACh release. When purine breakdown is experimentally down-regulated to mimicking the impaired purinergic pathway observed in pathological human bladders, endogenous ATP can markedly enhance detrusor contractility through activation of these receptors. Since P2X(3) blockade represents a potential therapeutic approach for diseases of the urinary tract, isolated porcine detrusor represents a reliable model for development of novel selective P2X(3) antagonists beneficial in the treatment of detrusor hyperactivity.