Overactive bladder--pharmacological aspects

Investigating Urine Biomarkers in Detrusor Underactivity and Detrusor Overactivity with Detrusor Underactivity Patients

Bladder inflammation and tissue hypoxia were considered important pathognomonic bladder features in detrusor underactivity (DU) and detrusor overactivity (DO) patients. This study investigated urine inflammatory and oxidative stress biomarker levels in DU and DO with DU (DO-DU) patients. Urine samples were collected from 50 DU and 18 DO-DU patients, as well as 20 controls. The targeted analytes included three oxidative stress biomarkers (8-OHdG, 8-isoprostane, and total antioxidant capacity [TAC]) and 33 cytokines. DU and DO-DU patients had different urine biomarker profiles from controls, including 8-OHdG, PGE2, EGF, TNFα, IL-1β, IL-5, IL-6, IL-8, IL-10, IL-17A, and CXCL10. Controlling for age and sex, multivariate logistic-regression models revealed that 8-OHdG, PGE2, EGF, IL-5, IL-8, IL-10, and TAC were significant biomarkers for diagnosing DU. In DU patients, urine TAC and PGE₂ levels were positively correlated with detrusor voiding pressure. In DO-DU patients, urine 8-OHdG, PGE₂, IL-6, IL-10, and MIP-1α levels were positively correlated with maximal urinary flow rate, while urine IL-5, IL-10, and MIP-1α were negatively correlated with the first sensation of bladder filling. Urine inflammatory and oxidative stress biomarker analysis provides a non-invasive and convenient approach for important clinical information in DU and DO-DU patients.

The five primary prostaglandins stimulate contractions and phasic activity of the urinary bladder urothelium, lamina propria and detrusor

Background

Inflammation is often associated with several bladder dysfunctions, including overactive bladder (OAB) and interstitial cystitis/bladder pain syndrome (IC/PBS). As such, inflammation of the bladder and the actions of inflammatory mediators may contribute to the development of urinary symptoms. This study assessed the actions of PGE₂, PGF₂, PGD₂, TXA₂, and PGI₂ on urinary bladder urothelium with lamina propria (U&LP), and detrusor smooth muscle.

Methods

Studies were carried out using isolated tissue baths, where strips of porcine bladder U&LP or detrusor were exposed to varying concentrations of prostaglandin agonists (1 μM and 10 μM).

Results

All assessed prostaglandin agonists contracted both the U&LP and detrusor smooth muscle, with the rank order of contractile response effectiveness as: PGE₂ > PGF_2α > TXA₂ > PGD₂ > PGI₂. In U&LP, treatment with PGE₂ (10 μM) increased tonic contractions by 1.36 ± 0.09 g (n = 42, p < 0.001) and phasic contractions by 40.4 ± 9.6% (n = 42, p < 0.001). In response to PGF_2α (10 μM), U&LP tonic contractions increased by 0.79 ± 0.06 g (n = 14, p < 0.001) and phasic activity by 13.3% ± 5.3% (n = 15, p < 0.05). In detrusor preparations, PGE₂ (10 μM) increased tonic contractions by 1.32 ± 0.13 g (n = 38, p < 0.001) and PGF_2α (10 μM) by 0.97 ± 0.14 g (n = 12, p < 0.001). Only 34% (n = 48) of all detrusor preparations exhibited spontaneous activity prior to the addition of any agonist at a frequency of 2.03 ± 0.12 cpm. In preparations that did not exhibit initial phasic activity, all of the prostaglandin agonists were capable of commencing phasic activity.

Conclusions

The urinary bladder U&LP and detrusor respond to a variety of prostaglandin agonists, with their activation resulting in direct contractions, as well as increases to spontaneous contractile activity. This study presents the prostaglandin receptor system as a potential therapeutic target for lower urinary tract dysfunction.

Afferent Pathway-Mediated Effect of α1 Adrenergic Antagonist, Tamsulosin, on the Neurogenic Bladder After Spinal Cord Injury

Purpose

The functions of the lower urinary tract (LUT), such as voiding and storing urine, are dependent on complex central neural networks located in the brain, spinal cord, and peripheral ganglia. Thus, the functions of the LUT are susceptible to various neurologic disorders including spinal cord injury (SCI). SCI at the cervical or thoracic levels disrupts voluntary control of voiding and the normal reflex pathways coordinating bladder and sphincter functions. In this context, it is noteworthy that α1-adrenoceptor blockers have been reported to relieve voiding symptoms and storage symptoms in elderly men with benign prostatic hyperplasia (BPH). Tamsulosin, an α1-adrenoceptor blocker, is also considered the most effective regimen for patients with LUT symptoms such as BPH and overactive bladder (OAB).

Methods

In the present study, the effects of tamsulosin on the expression of c-Fos, nerve growth factor (NGF), and nicotinamide adenine dinucleotide phosphate-diaphorase (NADPH-d) in the afferent micturition areas, including the pontine micturition center (PMC), the ventrolateral periaqueductal gray matter (vlPAG), and the spinal cord (L5), of rats with an SCI were investigated.

Results

SCI was found to remarkably upregulate the expression of c-Fos, NGF, and NADPH-d in the afferent pathway of micturition, the dorsal horn of L5, the vlPAG, and the PMC, resulting in the symptoms of OAB. In contrast, tamsulosin treatment significantly suppressed these neural activities and the production of nitric oxide in the afferent pathways of micturition, and consequently, attenuated the symptoms of OAB.

Conclusions

Based on these results, tamsulosin, an α1-adrenoceptor antagonist, could be used to attenuate bladder dysfunction following SCI. However, further studies are needed to elucidate the exact mechanism and effects of tamsulosin on the afferent pathways of micturition.

Effects of Saw Palmetto Extract on Urodynamic Parameters, Bladder Muscarinic and Purinergic Receptors and Urinary Cytokines in Rats with Cyclophosphamide-Induced Cystitis

OBJECTIVES

To clarify the effect of saw palmetto extract (SPE), a phytotherapeutic agent, on urodynamic parameters, bladder muscarinic and purinergic receptors, and urinary cytokines in rats with cystitis induced by cyclophosphamide (CYP).

METHODS

Saw palmetto extract (60 mg/kg per day) was administered orally twice a day for 7 days to rats. The urodynamic parameters in CYP (150 mg/kg i.p.)-treated rats were monitored by a cystometric method under anesthesia. The muscarinic and purinergic receptors in the bladder and submaxillary gland were measured by radioreceptor assays using [N-methyl-(3) H] scopolamine chloride([(3) H]NMS) and αβ-methylene-ATP [2,8-(3) H] tetrasodium salt ([(3) H]αβ-MeATP), respectively. Urinary cytokines (interleukin-1β [IL-1β], IL-6 and L-17) were measured with enzyme linked immunosorbent assay kits.

RESULTS

Micturition interval and micturition volume were significantly decreased and the frequency of micturition and basal pressure were significantly increased in the CYP-treated rats compared with sham-operated rats. Orally administered SPE significantly increased the micturition interval and micturition volume and decreased the frequency of micturition and basal pressure. The maximal number of sites (Bmax ) for the specific binding of [(3) H]NMS and [(3) H]αβ-MeATP was significantly decreased in the bladder. The decrease in receptors was attenuated by repeated treatment with SPE. An elevation in urinary cytokine (IL-1β and IL-17) levels were seen, and this increase was effectively suppressed by SPE treatment.

CONCLUSIONS

Saw palmetto extract attenuates the alteration of urodynamic parameters, pharmacologically relevant receptors, and urinary cytokines in CYP-treated rats. Therefore, SPE may be a potential therapeutic agent for improving the clinical symptoms of cystitis.

An animal study to compare the degree of the suppressive effects on the afferent pathways of micturition between tamsulosin and sildenafil

Background

Tamsulosin, an α1-adrenoceptor antagonist, and sildenafil, a phosphodiesterase (PDE) inhibitor, are reported to improve lower urinary tract symptoms including overactive bladder (OAB). This study is aimed at investing the effects of tamsulosin and sildenafil and comparing the degree of the suppressive effects on the afferent pathways of micturition between them using an animal model of OAB, the spontaneously hypertensive rat (SHR).

Results

The cystometric parameters, the basal pressure and duration of bladder contraction, were significantly increased in the SHR group as compared with the Wistar-Kyoto (WKY) group. The intercontraction interval also significantly decreased in the SHR group. In the SHR-Tam 0.01 mg/kg group and the SHR-Sil 1 mg/kg group, however, the basal pressure and duration were significantly reduced and the intercontraction interval was significantly prolonged. Moreover, the degree of the expression of c-Fos and NGF was significantly higher in the SHR group as compared with the WKY group. But it was significantly reduced in the SHR-Tam 0.01 mg/kg group and the SHR-Sil 1 mg/kg group. Furthermore, tamsulosin had a higher degree of effect as compared with sildenafil.

Conclusions

In conclusion, α1-adrenergic receptor antagonists and PDE-5 inhibitors may have an effect in improving the voiding functions through an inhibition of the neuronal activity in the afferent pathways of micturition.

The Role of Intra-abdominal Pressure Measurement in Awake Rat Cystometry

Rat cystometry is increasingly being used in research on overactive bladder and is a research tool for investigating bladder functions during the storage and voiding phases. Measurement of the pressure in the bladder is an essential part of cystometry, although that pressure is the sum of both detrusor and intra-abdominal pressures. In anesthetic cystometry, measurement of the intra-abdominal pressure is not necessary, because the values of this variable are negligible. In awake cystometry, however, it is mandatory to separate the changes in intra-abdominal pressure from those in intravesical pressure, because consciousness causes much variability in intra-abdominal pressure. This review describes why we use the term "detrusor overactivity" in animal research with intra-abdominal pressure and presents evidence for the role of intra-abdominal pressure in the cystometry of normal rats and in animal models of overactive bladder directed at understanding the pathogenesis of the overactive bladder condition. The methodology is also briefly reviewed.

Urothelial signaling

The urothelium, which lines the inner surface of the renal pelvis, the ureters, and the urinary bladder, not only forms a high-resistance barrier to ion, solute and water flux, and pathogens, but also functions as an integral part of a sensory web which receives, amplifies, and transmits information about its external milieu. Urothelial cells have the ability to sense changes in their extracellular environment, and respond to chemical, mechanical and thermal stimuli by releasing various factors such as ATP, nitric oxide, and acetylcholine. They express a variety of receptors and ion channels, including P2X3 purinergic receptors, nicotinic and muscarinic receptors, and TRP channels, which all have been implicated in urothelial-neuronal interactions, and involved in signals that via components in the underlying lamina propria, such as interstitial cells, can be amplified and conveyed to nerves, detrusor muscle cells, and ultimately the central nervous system. The specialized anatomy of the urothelium and underlying structures, and the possible communication mechanisms from urothelial cells to various cell types within the bladder wall are described. Changes in the urothelium/lamina propria ("mucosa") produced by different bladder disorders are discussed, as well as the mucosa as a target for therapeutic interventions.

The effects of α-defensin 1 on electrical field stimulation-induced contraction of rat bladders

This study was designed to investigate the effects of α-defensin 1 on electrical field stimulation (EFS)-induced contractions in isolated rat bladder detrusor muscles. We evaluated the effects of α-defensin 1 (50 pM∼5 nM) on EFS-induced contractions in the detrusor smooth muscles from 35 rats (2-30 Hz). Bladder strips were pretreated with α-defensin 1 and then changes of contractions by adenosine 5'-triphosphate (ATP) were observed. Moreover, after pretreatment with α-defensin 1 for 10 min, changes in concentration-response curves to hydrogen peroxide (H2O2) were investigated. Alpha-defensin 1 has increased EFS-induced contractions, significantly, and the contractile response to ATP (1,2,5,10mM) was also increased significantly when strips were pretreated with α-defensin 1. In addition, alpha-defensin 1 increased H2O2-induced contractions. The present study demonstrates that α-defensin 1 increases EFS-induced contractions of rat detrusor muscles via purinergic contraction coupled with the Rho kinase pathway.

Coupled nitric oxide and autonomic receptor functional responses in the normal and inflamed urinary bladder of the rat

Both divisions of the autonomic nervous system are involved in regulation of urinary bladder function. Several substances, other than noradrenaline and acetylcholine, seem to play important roles in physiology and pathophysiology of lower urinary tract. In the current study, we aimed to examine if there exist interplays between nitric oxide (NO) and autonomic transmitters and if such interactions vary in different parts of the urinary bladder in healthy and cyclophosphamide (CYP)-induced cystitic rats; when administered to the animals (100 mg/kg; i.p.), the cytotoxic CYP metabolite acrolein induces bladder inflammation. In the current study a series of in vitro functional studies were performed on detrusor muscle strip preparations. Stimulation with electrical field stimulation (EFS), methacholine, adenosine 5´-triphosphate (ATP), and adrenaline evoked contractile responses in isolated bladder preparations that were significantly reduced in cyclophosphamide (CYP)-treated rats. While the nitric oxide synthase inhibitor N(omega)-nitro-L-arginine (L-NNA; 10(-4) M) did not affect contractile responses in normal, healthy strip preparations, it significantly increased the contractile responses to EFS, methacholine and adrenaline, but not to ATP, in the bladders from the CYP-treated rats. In the CYP-treated rats, the ATP-evoked relaxatory part of its dual response (an initial contraction followed by a relaxation) was 6-fold increased in comparison with that of normal preparations, whereas the isoprenaline relaxation was halved in the CYP-treated. While L-NNA (10(-4) M) had no effect on the isoprenaline-evoked relaxations, it reduced the ATP-evoked relaxations in strip preparations from the bladder body of CYP-treated rats. Stimulation of beta(2)- and beta(3)-adrenoceptors evoked relaxations and both responses were reduced in cystitis, the latter to a larger extent. In the trigone, the reduced ATP-evoked contractile response in the inflamed strips was increased by L-NNA, while L-NNA had no effect on the ATP-evoked relaxations, neither on the relaxations in healthy nor on the larger relaxations in the inflamed trigone. The study shows that both contractile and relaxatory functions are altered in the state of inflammation. The parasympathetic nerve-mediated contractions of the body of the bladder, evoked by the release of ATP and acetylcholine, were substantially reduced in cystitis. The relaxations to beta-adrenoceptor and purinoceptor stimulation were also reduced but only the ATP-evoked relaxation involved NO.

Effects of Tamsulosin on Urinary Bladder Function and Neuronal Activity in the Voiding Centers of Rats with Cyclophosphamide-induced Overactive Bladder

PURPOSE

The overactive bladder (OAB) syndrome is characterized by urgency usually with frequency and nocturia. Tamsulosin, α(1)-adrenergic receptor antagonist, is widely used to reduce symptoms of urinary obstruction and prostatic hyperplasia. Tamsulosin can across the blood-brain barrier. We investigated the effects of tamsulosin on the symptoms of OAB in relation to neuronal activity using rats.

METHODS

Adult female Sprague-Dawley rats, weighing 250±10 g (9 weeks old), were used in this study. The animals were divided into five groups (n=8 in each group): control group, OAB-induced group, OAB-induced and 0.01 mg/kg tamsulosin-treated group, OAB-induced and 0.1 mg/kg tamsulosin-treated group, and OAB-induced and 1 mg/kg tamsulosin-treated group. OAB was induced by intraperitoneal injection of cyclophosphamide (75 mg/kg) every third day for 10 days. The rats in the tamsulosin-treated groups orally received tamsulosin once a day for 14 consecutive days at the respective dose of the groups, starting 1 day after the induction of OAB. Cystometry for bladder pressure determination, immunohistochemistry for c-Fos, nicotinamide adenine dinucleotide phosphate-diaphorase histochemistry for nitric oxide synthase (NOS) in the neuronal voiding centers and western blot for inducible NOS in the bladder were conducted.

RESULTS

Cyclophosphamide injection enhanced contraction pressure and time, representing the induction of OAB. Contraction pressure and time were significantly suppressed by tamsulosin treatment. c-Fos and NOS expressions in the neuronal voiding centers were enhanced by induction of OAB. OAB-induced c-Fos and NOS expressions were suppressed by tamsulosin treatment.

CONCLUSIONS

Tamsulosin exerts inhibitory effect on neuronal activation in the neuronal voiding centers of OAB. The present results suggest the possibility that tamsulosin is effective therapeutic modality for ameliorating the symptoms of OAB.

Antimuscarinics suppress adenosine triphosphate and prostaglandin E2 release from urothelium with potential improvement in detrusor overactivity in rats with cerebral infarction

PURPOSE

Antimuscarinics improve detrusor overactivity. We evaluated the effects and action mechanisms of imidafenacin (Kyorin Pharmaceutical, Tokyo, Japan), a novel therapeutic agent for overactive bladder with antimuscarinic activity, on mediator release from urothelium and detrusor overactivity induced by cerebral infarction.

MATERIALS AND METHODS

Bladder hydrodistention was achieved by intravesical infusion of Krebs solution. Bladder adenosine triphosphate and prostaglandin E(2) were measured in the presence and absence of anticholinergics using luciferin-luciferase assay and enzyme-linked immunoassay, respectively. Cerebral infarction was induced in rats by occluding the left middle cerebral artery. The effects of intravenous imidafenacin on bladder function were examined using cystometry in rats with cerebral infarction and in those pretreated with resiniferatoxin.

RESULTS

Increased intravesical adenosine triphosphate and prostaglandin E(2) were shown by induced distention of isolated rat bladders. Imidafenacin and darifenacin (Kemprotec, Middlesbrough, United Kingdom) significantly suppressed the increases in adenosine triphosphate and prostaglandin E(2). Decreased bladder capacity was observed in rats with cerebral infarction. Detrusor overactivity was suppressed with a minimum intravenous dose of 0.001 mg/kg imidafenacin. The effects of imidafenacin were not noted in rats pretreated with resiniferatoxin.

CONCLUSIONS

Results support the hypothesis or suggest that imidafenacin improves cerebral infarction induced detrusor overactivity by suppressing peripheral C-fibers. This effect is thought to be associated with suppression of the release of adenosine triphosphate and prostaglandin E(2) from the urothelium.

Role of Purinergic Signaling in Voiding Dysfunction

Purinergic signaling is a term that relates to adenosine triphosphate binding to its receptor (purinergic receptors such as P2X and P2Y subtypes). This pathway has been implicated in bladder functional disorders related to interstitial cystitis/painful bladder syndrome, neurogenic bladder secondary to spinal cord injury, lower urinary tract symptoms, diabetes, and aging. Purinergic signaling occurs at multiple sites, including the central nervous system, peripheral motor and sensory nerves, detrusor smooth muscle, and bladder urothelium. Future pharmacologic agents to treat bladder functional disorders may be able to target purinergic signaling at one or more of these sites.

Loss of muscarinic and purinergic receptors in urinary bladder of rats with hydrochloric acid-induced cystitis

OBJECTIVES

To clarify the basic mechanism involved in the pathophysiology of cystitis by characterizing the urodynamic parameters, pharmacologically relevant (muscarinic and purinergic) receptors, and the in vivo release of adenosine triphosphate (ATP) in the bladder of hydrochloric acid (HCl)-treated rats.

METHODS

The muscarinic and purinergic receptors in rat tissue were measured by radioreceptor assays using (N-methyl-³H) scopolamine methyl chloride ([³H]NMS) and αβ-methylene-ATP (2,8-³H) tetrasodium salt ([³H]αβ-MeATP), respectively. The urodynamic parameters and ATP levels were measured using a cystometric method and the luciferin-luciferase assay, respectively.

RESULTS

In the HCl-treated rats, the micturition interval and micturition volume were significantly (48% and 55%, respectively, P <.05) decreased and the number of micturitions was significantly (3.2-fold, P <.05) increased compared with those of the control rats. The maximal number of binding sites for [³H]NMS and [³H]αβ-MeATP was significantly (55% and 72%, respectively, P <.001) decreased in the bladder of HCl-treated rats, suggesting downregulation of both muscarinic and purinergic receptors. In the HCl-treated rats, the inhibition constant, K(i), values for oxybutynin, solifenacin, and darifenacin were significantly (1.3-1.4-fold, P <.05) increased, but those for tolterodine and AF-DX116 were unchanged. Similarly, the inhibition constant for A-317491, pyridoxal-phosphate-6-azophenyl-2',4'-disulfonic acid tetrasodium, and MRS2273 was significantly (5.5, 11, and 7.6-fold, respectively, P <.001) increased. Furthermore, the in vivo release of ATP was significantly (P <.05) enhanced in the HCl-treated rat bladder.

CONCLUSIONS

Both muscarinic and purinergic mechanisms might be, at least in part, associated with the urinary dysfunction due to cystitis.

Urodynamic Effects of Propiverine on Detrusor Overactivity and Abdominal Straining during Voiding in Awake Rats with Intravesical Prostaglandin E2Instillation

Purpose

We investigated the effect of propiverine on cystometric parameters based on intraabdominal pressure (IAP) in awake rats in an overactive bladder (OAB) model induced by intravesical instillation of prostaglandin E₂ (PGE₂).

Materials and Methods

Twenty-two female Sprague-Dawley rats were used. Polyethylene catheters were implanted into the bladder to record the intravesical pressure (IVP) and into the femoral artery to administer medication. A balloon-fitted catheter was positioned in the abdominal cavity to record the IAP. Awake cystometries were performed before and after intraarterial administration of propiverine 1 mg/kg (n=6), intravesical administration of 50µM PGE₂ only (n=6), or intravesical PGE₂ plus 1 mg/kg (n=4) or 3 mg/kg (n=6) of intraarterial propiverine. Cystometric pressure and volume parameters and variables related to detrusor overactivity (DO) were investigated.

Results

Rats administered intravesical PGE₂ showed increased pressure parameters and decreased volume parameters comparable to the DO model, which was effectively prevented by propiverine (1 or 3 mg/kg). Typical DO shown during the filling phase was decreased by intraarterial propiverine (3 mg/kg) injection. After propiverine (3 mg/kg) injection, IAP was increased at the time of micturition pressure with or without threshold pressure (p<0.05, p<0.01) depending on the dose administered.

Conclusions

Propiverine improved pressure- and volume-related parameters in an OAB model. Furthermore, it also decreased the frequency of DO. However, higher concentrations of propiverine induced straining voiding.

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.

The effect of darifenacin on overactive bladders in female and male rabbits

Our current study utilized a model of bladder instability to compare the effectiveness of darifenacin, a selective m3 muscarinic antagonist, at inhibiting overactive bladder (OAB) dysfunction in both male and female rabbits. Twenty-four male and female NZ white rabbits were used for this experiment. Each rabbit was anesthetized and the carotid artery was cannulated for blood pressure (BP) monitoring and the left femoral artery was cannulated for acetylcholine (Ach) administration. The bladder dome was catheterized for monitoring bladder pressure and for cystometry. A ligature was placed around the urethra just distal to the bladder to induce OAB. After OAB developed, the response to four IV doses of darifenacin (0.003; 0.01; 0.03; 0.09 mg/kg) evaluated for their effects. Darifenacin: (1) was an equally potent inhibitor of the contractile response of both sexes to intra-arterial Ach, (2) had no effects on BP, (3) was a potent inhibitor of the frequency of OAB, but had a significantly less potent effect on the amplitude, and (4) Darifenacin showed a greater potency in the female rabbits than in the males. These studies provide support for the use of darifenacin in the treatment of OAB.

Cholinergic nitric oxide release from the urinary bladder mucosa in cyclophosphamide-induced cystitis of the anaesthetized rat

BACKGROUND AND PURPOSE

Previous reports have suggested that nitric oxide (NO) may be released by cholinergic stimuli in the rat bladder in cyclophosphamide-induced cystitis, affecting bladder function. In the current study, we evaluated the effects of cyclophosphamide-induced cystitis on muscarinic whole bladder contractile responses in vivo, and further, if NO might be released from the mucosa by cholinergic stimuli.

EXPERIMENTAL APPROACH

Male rats were pre-treated either with cyclophosphamide (100 mg kg(-1); to induce cystitis) or saline (serving as controls). 60 h later, rats were anaesthetized and bladder pressure monitored.

KEY RESULTS

The muscarinic receptor agonist methacholine (MeCh; 0.5-5 microg kg(-1) i.v.) induced similar contractions (i.e. bladder pressure increases) in inflamed bladders as in controls, which were attenuated dose-dependently by the muscarinic M1/M3/M5 antagonist 4-diphenylacetoxy-N-methylpiperidine (4-DAMP; 0.1-1000 microg kg(-1) i.v.). In inflamed bladders, the cholinergic bladder contractions were enhanced after removing the mucosa, while cholinergic contractions were similar in intact and urothelium-denuded inflamed bladders in the presence of the NO synthase inhibitor N(omega)-nitro-L-arginine methyl ester (L-NAME; 30 mg kg(-1) i.v.). L-NAME attenuated the antagonistic effect of 4-DAMP on MeCh-induced contractions in intact inflamed bladders. However L-NAME did not affect the antagonism by 4-DAMP of MeCh-induced contractions of urothelium-denuded bladders, under control conditions or with cyclophosphamide-induced cystitis.

CONCLUSIONS AND IMPLICATIONS

In cyclophosphamide-induced cystitis, the cholinergic function of the bladder is altered. In the inflamed bladder, NO seems to be released via cholinergic stimuli through mucosal muscarinic M3/M5 receptors, presumably on urothelial cells, affecting bladder function.

Aging impairs neurogenic contraction in guinea pig urinary bladder: role of oxidative stress and melatonin

The incidence of urinary bladder disturbances increases with age, and free radical accumulation has been proposed as a causal factor. Here we investigated the association between changes in bladder neuromuscular function and oxidative stress in aging and the possible benefits of melatonin treatment. Neuromuscular function was assessed by electrical field stimulation (EFS) of isolated guinea pig detrusor strips from adult and aged female guinea pigs. A group of adult and aged animals were treated with 2.5 mg·kg−1·day−1 melatonin for 28 days. Neurotransmitter blockers were used to dissect pharmacologically the EFS-elicited contractile response. EFS induced a neurogenic and frequency-dependent contraction that was impaired by aging. This impairment is in part related to a decrease in detrusor myogenic contractility. Age also decreased the sensitivity of the contraction to pharmacological blockade of purinergic and sensitive fibers but increased the effect of blockade of nitrergic and adrenergic nerves. The density of cholinergic and nitrergic nerves remained unaltered, but aging modified afferent fibers. These changes were associated with an increased level of markers for oxidative stress. Melatonin treatment normalized oxidative levels and counteracted the aging-associated changes in bladder neuromuscular function. In conclusion, these results show that aging modifies neurogenic contraction and the functional profile of the urinary bladder plexus and simultaneously increases the oxidative damage to the organ. Melatonin reduces oxidative stress and improves the age-induced changes in bladder neuromuscular function, which could be of importance in reducing the impact of age-related bladder disorders.

Qualitative and quantitative expression profile of muscarinic receptors in human urothelium and detrusor

PURPOSE

We compared the complete spectrum of receptor subtypes expressed by human detrusor and its primary culture with the expression profile in a human urothelium immortalized cell line, and in fresh urothelium tissue and its primary cell culture.

MATERIALS AND METHODS

The levels of mRNA expressed for receptor subtypes M1 through M5 were determined with reverse transcriptase-polymerase chain reaction and quantitative polymerase chain reaction in total RNA extracted individually from different human bladder specimens, including fresh tissue of human urothelium and detrusor, and their respective primary cultures, as well as from the UROtsa cell line.

RESULTS

All 5 muscarinic receptors were detected in fresh human bladder tissue by reverse transcriptase-polymerase chain reaction RNA. The same was true in separated urothelium and detrusor tissue except for the lack of the M5 receptor transcript. Receptor subtype mRNA expression in the UROtsa cell line paralleled expression in fresh human bladder. Quantitative polymerase chain reaction data further corroborated these results and showed comparable mRNA expression for M2 and M3 in primary detrusor cultures. Primary cultures also had a decreased copy number of receptor genes than native tissue. The decrease was even more pronounced in primary urothelium culture and the UROtsa cell line in the presence of high calcium. M2 and M3 receptors were also detected in urothelium and detrusor by immunoreactivity.

CONCLUSIONS

We identified all 5 existing muscarinic receptor subtypes in detrusor and urothelium, and transcripts levels of M2 and M3 were comparable in detrusor. These results support an alternative site of action in urothelium for anti-muscarinic drugs. Urothelial receptors should be considered in the design of future drugs for overactive bladder.

Purinergic P2 receptors as targets for novel analgesics

Following hints in the early literature about adenosine 5'-triphosphate (ATP) injections producing pain, an ion-channel nucleotide receptor was cloned in 1995, P2X3 subtype, which was shown to be localized predominantly on small nociceptive sensory nerves. Since then, there has been an increasing number of papers exploring the role of P2X3 homomultimer and P2X2/3 heteromultimer receptors on sensory nerves in a wide range of organs, including skin, tongue, tooth pulp, intestine, bladder, and ureter that mediate the initiation of pain. Purinergic mechanosensory transduction has been proposed for visceral pain, where ATP released from epithelial cells lining the bladder, ureter, and intestine during distension acts on P2X3 and P2X2/3, and possibly P2Y, receptors on subepithelial sensory nerve fibers to send messages to the pain centers in the brain as well as initiating local reflexes. P1, P2X, and P2Y receptors also appear to be involved in nociceptive neural pathways in the spinal cord. P2X4 receptors on spinal microglia have been implicated in allodynia. The involvement of purinergic signaling in long-term neuropathic pain and inflammation as well as acute pain is discussed as well as the development of P2 receptor antagonists as novel analgesics.

Evaluation of two techniques of partial urethral obstruction in the male rat model of bladder outlet obstruction

OBJECTIVES

To perform a comparison to determine which of two methods of partial urethral ligation produces the most consistent outcome and fewest side effects. Such a study has not been previously reported. Partial urethral ligation is a means of causing reproducible bladder outlet obstruction. In the male rat model, partial urethral obstruction can be performed either by perineal incision and bulbous urethral ligation or retropubic incision and midprostatic obstruction.

METHODS

Fifteen male Sprague-Dawley rats were studied. Five were selected for bulbous urethral obstruction through a perineal incision, five for midprostatic obstruction using a retropubic approach, and five for a sham operation through a perineal incision.

RESULTS

The operative time was shorter and morbidity lower with the perineal approach compared with the retropubic approach. Inflammation or infection, or both, were seen in the prostate, bladder, proximal urethra, ureters, and kidneys in the rats in which a midprostatic obstruction was performed. The proximal urethra and prostate were mildly inflamed in those rats that underwent bulbous obstruction. Sham-operated rats exhibited mild prostatitis only.

CONCLUSIONS

The perineal approach to the bulbous urethra is the method of choice for creating a partial urethral obstruction model of bladder outlet obstruction in the male rat.

Altered muscarinic receptor subtype expression and functional responses in cyclophosphamide induced cystitis in rats

In the in vitro study, it was investigated whether the expression of muscarinic receptors and cholinergic responses were altered in the situation of experimental cystitis. Rats were treated with cyclophosphamide intraperitoneally and the bladders were excised 36-100 h later. Immunohistochemistry and immunoblotting showed all subtypes of the muscarinic receptor (M1-M5) to be present in the specimens from inflamed urinary bladders and controls. In the cyclophosphamide-treated rats, the expression of muscarinic M5 receptors was increased by more than 40 times (p<0.01; n=8) both in the smooth muscle and the urothelium. Both the maximal contractile response to carbachol and to a high potassium concentration was approximately halved in cyclophosphamide-treated tissues, whereas the reduction was substantially greater in response to low carbachol concentrations (<EC(50)). The administration of 4-DAMP inhibited the carbachol-induced contractile responses of inflamed strips less potently than of controls, whereas pirenzepine and methoctramine showed equipotency in the two groups. The nitric oxide synthase inhibitor l-NNA increased the contractile effect of carbachol in inflamed detrusor strips, while it had no effect in controls. Immunoblotting showed endothelial nitric oxide synthase (eNOS) to be up-regulated in cystitis, and immunohistochemistry revealed the change to occur in the urothelium and in the suburothelial layer. The alteration of cholinergic detrusor responses in cyclophosphamide-treated rats depends mainly on a general detriment of contractility but also on indirect effects possibly via nitric oxide synthesis. The most prominent histological alterations occurred in the urothelium in which muscarinic M5 receptors increased in particular. The study further underlines that the urothelium may play significant roles in the pathogenesis of urinary bladder disorders such as interstitial cystitis.

Management of detrusor dysfunction in the elderly: changes in acetylcholine and adenosine triphosphate release during aging

Numerous studies have detailed age-related changes in the structure and function of the bladder that may contribute to the high prevalence of overactive bladder (OAB) in the elderly population, but the relation of these changes to OAB symptoms remains unclear. Physiologic and neurochemical studies have been conducted in human detrusor strips obtained from people of different ages, focusing on potential changes in cholinergic and purinergic neurotransmission, as well as the release and actions of acetylcholine (ACh) from nonneuronal bladder cells. Results from physiologic and microdialysis experiments indicate that purinergic transmission increases with age, whereas cholinergic transmission decreases. These effects are most likely because of decreased release of ACh and increased release of adenosine triphosphate (ATP) from postganglionic parasympathetic axons innervating the bladder. Immunohistochemical experiments showed that choline acetyltransferase in the human detrusor is contained not only in parasympathetic axons, but also in cells of the urothelium. The release of nonneuronal ACh increases with age and detrusor stretch. The age-related increase in purinergic transmission in the detrusor and other data indicating that responses to ATP are increased in detrusor overactivity suggest that purinergic receptor antagonists may provide a useful complement to muscarinic receptor antagonists in the treatment of older patients with OAB. Nonneuronal ACh release may play a key role in the storage phase of the micturition reflex, and this may explain, at least in part, the effectiveness of antimuscarinic agents for the treatment of OAB.

Inhibition of Hyperreflexia by Vaginally Administered Oxybutynin: A Novel Rabbit Model

PURPOSE

The rabbit has proved to be an excellent model in which to study lower urinary tract function and pathological mechanisms involved in specific forms of lower urinary tract dysfunctions, including those involved with partial outlet obstruction (benign prostatic hyperplasia), erectile dysfunction, bladder instability and ischemic bladder disease. The current study describes a model of bladder instability induced in female rabbits and its use in developing a novel form of vaginal treatment for this instability.

MATERIALS AND METHODS

A total of 18 female New Zealand White rabbits were used for this experiment. Each rabbit was anesthetized and the carotid artery was cannulated for blood pressure monitoring. The bladder dome was catheterized for monitoring bladder pressure and for cystometry. A ligature was placed around the urethra just distal to the bladder neck to prevent leakage through the urethra and generate unstable bladder contractions. After initial cystometry the bladder was emptied and then filled to 30 ml. Acetylcholine (Ach) was administered into the vesical artery at 15-minute intervals for 2 hours. Hyperreflexia usually developed within 30 minutes. Vaginal oxybutynin (low and high dose) was applied and the effect on cystometry, the response to Ach, and the amplitude and frequency of hyperreflexia was determined.

RESULTS

Each dose of oxybutynin increased bladder capacity and improved compliance. The high oxybutynin dose completely inhibited the response to Ach and significantly decreased micturition pressure. The high dose decreased uninhibited bladder contraction peak pressure in a time dependent manner to a greater extent than it decreased uninhibited contraction frequency. The low dose of oxybutynin had no effect on micturition pressure, significantly inhibited the response to Ach and hyperreflexia amplitude to approximately 40% of control values, and had little effect on hyperreflexia frequency.

CONCLUSIONS

Vaginally delivered oxybutynin was effective in improving bladder compliance, inhibiting intra-arterial Ach stimulated bladder contractions and significantly decreasing the amplitude of hyperreflexia. Vaginal oxybutynin had a more potent effect on the evoked response to Ach and on hyperreflexia than it did on micturition pressure.

Diagnosis and treatment of the overactive bladder

Overactive bladder syndrome (OAB) is a symptomatic diagnosis based on the presence of urgency, with or without urge incontinence, and usually accompanied by frequency and nocturia, in the absence of obvious pathologic or metabolic disease. Initial management of OAB requires an integrated approach using behavioral and pharmacologic methods. Patients should be educated about the functioning of the lower urinary tract system, fluid and dietary management, timed or prophylactic voiding and bladder training regimens, the keeping of micturition charts or bladder diaries, and pelvic floor exercises. Although the effectiveness of muscarinic receptor antagonists for the treatment of OAB has been shown, adverse effects, such as dry mouth, constipation, and blurred vision have somewhat limited their usefulness. Newer agents that are more bladder selective have been and continue to be developed. The concept of clinical effectiveness-a combination of efficacy, tolerability, and compliance-can be used to evaluate not only how well a drug works, but also the side-effect profile and bothersomeness and how likely patients are to continue treatment. Patients who do not respond to antimuscarinic treatment of OAB may do so because of a variety of nonpharmacologic and pharmacologic reasons. Most cases of OAB are not cured, but rather the symptoms are reduced, with an associated improvement in the patients' quality of life. Patients who have failed behavioral and pharmacologic intervention may respond to neuromodulation and augmentation cystoplasty. Future approaches may include (1) other types of systemic pharmacologic therapy; (2) intravesical administration of drugs, including blockers of afferent input; (3) intradetrusor injection of botulinum toxin; (4) the use of tissue engineering to simplify augmentation cystoplasty; (5) genetic interventions to reverse neuroplasticity changes; and (6) combinations of these approaches.