Bladder Contractions In Rats Research Articles

126 - L-DOPA has a possible role in inhibition of the rat bladder contraction

126 - L-DOPA has a possible role in inhibition of the rat bladder contraction

The effects of agomelatine, fluoxetine, and sertraline on rat bladder contraction in vitro

The effects of agomelatine, fluoxetine, and sertraline on rat bladder contraction in vitro

The frequency spectrum of bladder non-voiding activity as a trigger-event for conditional stimulation: Closed-loop inhibition of bladder contractions in rats.

To test the hypothesis that the frequency of bladder non-voiding contractions (NVCs) can be used as a trigger event for closed-loop conditional inhibition of detrusor contractions via tibial nerve (TN) or dorsal penile nerve (DPN) stimulation. In urethane anaesthetized male Wistar rats, the bladder was filled continuously with saline to evoke contractions. To test the plausibility of conditional inhibition via the TN, electrical stimulation was switched on manually when the pressure increased above a threshold of 10 cmH2 0 above the baseline. For testing conditional stimulation via the DPN, the pressure signal was continuously stored and a baseline threshold, the area under the curve (AUC) of the amplitude spectrum in the 0.2-20 Hz range of a 5 s window at the beginning of filling was calculated. When the AUC of subsequent pressure windows superseded the baseline threshold, the DPN was automatically stimulated. TN stimulation failed to inhibit evoked voiding contractions. The NVC frequency spectrum based DPN stimulation successfully inhibited 70% of the evoked contractions and resulted in a 45% increase in bladder capacity (BC). While, conditional TN stimulation failed to suppress bladder contractions, DPN stimulation, automatically triggered by an increased frequency of bladder non-voiding activity, resulted in bladder inhibition, and a consequential increase in BC. This study demonstrates the plausibility of using the frequency of NVCs as a trigger event for conditional inhibition of detrusor contractions.

Feasibility of deep brain stimulation for controlling the lower urinary tract functions: An animal study

ObjectiveTo evaluate the feasibility of deep brain stimulation (DBS) and compare the potential of four DBS targets in rats for regulating bladder activity: the periaqueductal gray (PAG), locus coeruleus (LC), rostral pontine reticular nucleus (PnO), and pedunculopontine tegmental nucleus (PPTg). MethodsA bipolar stimulating electrode was implanted. The effects of DBS on the inhibition and activation of micturition reflexes were investigated by using isovolumetric intravesical pressure recordings. ResultsPAG DBS at 2–2.5 V, PnO DBS at 2–2.5 V, and PPTg DBS at 1.75–2.5 V nearly completely inhibited reflexive isovolumetric bladder contractions. By contrast, LC DBS at 1.75 and 2 V slightly augmented reflexive isovolumetric bladder contractions in rats. DBSs on PnO and PPTg at higher intensities (2.5–5 V) demonstrated a higher success rate and larger contraction area evocation in activating bladder contractions in a partially filled bladder. DBS targeting the PPTg was most efficient in suppressing reflexive isovolumetric bladder contractions. ConclusionPPTg DBS demonstrated stable results and high potency for controlling bladder contractions. PPTg might be a promising DBS target for developing new neuromodulatory approaches for the treatment of bladder dysfunctions. SignificanceDBS could be a potential approach to manage bladder function under various conditions.

Synthesis and optimization of novel α-phenylglycinamides as selective TRPM8 antagonists

Transient receptor potential melastatin 8 (TRPM8) is activated by innocuous cold and chemical substances, and antagonists of this channel have been considered to be effective for pain and urinary diseases. N-(3-aminopropyl)-2-{[(3-methylphenyl)methyl]oxy}-N-(2-thienylmethyl)benzamide hydrochloride (AMTB), a TRPM8 antagonist, was proposed to be effective for overactive bladder and painful bladder syndrome; however, there is a potential risk of low blood pressure. We report herein the synthesis and structure–activity relationships of novel phenylglycine derivatives that led to the identification of KPR-2579 (20l), a TRPM8 selective antagonist. KPR-2579 reduced the number of icilin-induced wet-dog shakes and rhythmic bladder contraction in rats, with no negative cardiovascular effects at the effective dose.

Identification and bioactivity evaluation of a novel bradykinin inhibitory peptide from the skin secretion of Chinese large odorous frog, Odorrana livida.

A novel peptide was isolated from the skin secretion of Chinese large odorous frog, Odorrana livida, and was named as Rana-BI. The cDNA sequencing was obtained by 'shotgun' cloning. The amino acid sequence of the mature peptide was identified as Gly-Leu-Leu-Ser-Gly-Lys-Ser-Val-Lys-Gly-Ser-Ile-OH by automated Edman degradation, and the molecular weight of the peptide was confirmed to be 1144.68 Da by MALDI-TOF and liquid chromatography/MS. Subsequently, the bioactivity of synthetic peptide was evaluated by smooth muscle assay using isolated rat bladder preparation. It was demonstrated that Rana-BI inhibited the contraction of rat bladder induced by bradykinin. Comparing with other peptides by searching from database, the primary structure of Rana-BI showed high similarity with that of an antimicrobial peptide of Rana family (12/12 residues). These data revealed a novel biological function of this peptide.

(18F)FDG-PET brain imaging during the micturition cycle in rats detects regions involved in bladder afferent signalling

BackgroundThis feasibility study established an experimental protocol to evaluate brain activation patterns using fluorodeoxyglucose positron emission tomography ((18F)FDG-PET) during volume-induced voiding and isovolumetric bladder contractions in rats.MethodsFemale Sprague-Dawley rats were anaesthetized with urethane and underwent either volume-induced voiding cystometry or isovolumetric cystometry and simultaneous functional PET brain imaging after injection of (18F)FDG in the tail vein. Brain glucose metabolism in both groups was compared to their respective control conditions (empty bladder). Relative glucose metabolism images were anatomically standardized to Paxinos space and analysed voxel-wise using Statistical Parametric Mapping 12 (SPM12).ResultsDuring volume-induced voiding, glucose hypermetabolism was observed in the insular cortex while uptake was decreased in a cerebellar cluster and the dorsal midbrain. Relative glucose metabolism during isovolumetric bladder contractions increased in the insular and cingulate cortices and decreased in the cerebellum.ConclusionsOur findings demonstrate that volume-induced voiding as well as isovolumetric bladder contractions in rats provokes changes in brain metabolism, including activation of the insular and cingulate cortices, which is consistent with their role in the mapping of bladder afferent activity. These findings are in line with human studies. Our results provide a basis for further research into the brain control of the lower urinary tract in small laboratory animals.

Modulation of nerve-evoked contractions by β3-adrenoceptor agonism in human and rat isolated urinary bladder

Activation of β3-adrenoceptors has been shown to have a direct relaxant effect on urinary bladder smooth muscle from both rats and humans, however there are very few studies investigating the effects of β3-adrenoceptor agonists on nerve-evoked bladder contractions. Therefore in the current study, the role of β3-adrenoceptors in modulating efferent neurotransmission was evaluated. The effects of β3-adrenoceptor agonism on neurogenic contractions induced by electrical field stimulation (EFS) were compared with effects on contractions induced by exogenous acetylcholine (Ach) and αβ-methylene adenosine triphosphate (αβ-meATP) in order to determine the site of action. Isoproterenol inhibited EFS-induced neurogenic contractions of human bladder (pD2=6.79; Emax=65%). The effect of isoproterenol was selectively inhibited by the β3-adrenoceptor antagonist L-748,337 (pKB=7.34). Contractions induced by exogenous Ach (0.5–1μM) were inhibited 25% by isoproterenol (3μM) while contractions to 10Hz in the same strip were inhibited 67%. The selective β3-adrenoceptor agonist CL-316,243 inhibited EFS-induced neurogenic contractions of rat bladder (pD2=7.83; Emax=65%). The effects of CL-316,243 were inhibited in a concentration dependent manner by L-748,337 (pA2=6.42). Contractions induced by exogenous Ach and αβ-meATP were significantly inhibited by CL-316,243, 29% and 40%, respectively. These results demonstrate that the activation of β3-adrenoceptors inhibits neurogenic contractions of both rat and human urinary bladder. Contractions induced by exogenously applied parasympathetic neurotransmitters are also inhibited by β3-agonism however the effect is clearly less than on neurogenic contractions (particularly in human), suggesting that in addition to a direct effect on smooth muscle, activation of prejunctional β3-adrenoceptors may inhibit neurotransmitter release.

Bradykinin Contracts Rat Urinary Bladder Largely Independently of Phospholipase C

Several receptor systems in the bladder causing detrusor smooth muscle contraction stimulate phospholipase C (PLC). PLC inhibition abolishes bladder contraction via P2Y6 but not that via M3 muscarinic receptors, indicating a receptor-dependent role of PLC. Therefore, we explored the role of PLC in rat bladder contraction by bradykinin. The PLC inhibitor U 73,122 [1-(6-[([17β]-3-methoxyestra-1,3,5[10]-trien-17-yl)-amino]hexyl)-1H-pyrrole-2,5-dione] did not affect the bradykinin response to a significantly greater degree than its inactive analog U 73,343 [10 μM each; 1-(6-[-([17β]-3-methoxyestra-1,3,5[10]-trien-17-yl)-amino]hexyl)-2,5-pyrrolidinedione], whereas the phospholipase D inhibitor butan-1-ol relative to its inactive control butan-2-ol caused a weak but significant inhibition (0.3% each). The cytosolic phospholipase A2 inhibitor arachidonyltrifluoromethyl ketone (300 μM) and the cyclooxygenase inhibitor indomethacin (10 μM) caused strong inhibition of the bradykinin response. The L-type Ca(2+) channel blocker nifedipine (10-100 nM) concentration-dependently caused strong inhibition, whereas only a small but significant inhibition was seen with SK&F 96,365 [10 μM; 1-[β-[3-(4-methoxyphenyl)propoxy]-4-methoxyphenethyl]-1H-imidazole HCl], an inhibitor of receptor-operated Ca(2+) channels. Several protein kinase C inhibitors yielded an equivocal picture (inhibition by 10 μM bisindolylmaleimide I and 1 μM calphostin but not by 10 μM chelerythrine). The rho kinase inhibitor Y 27,632 [1-10 μM; trans-4-[(1R)-1-aminoethyl]-N-4-pyridinylcyclohexanecarboxamide] caused a strong and concentration-dependent inhibition of the bradykinin response. Our data support that not only M3 but also bradykinin receptors cause bladder contraction by a largely PLC-independent mechanism. Both responses strongly involve L-type Ca(2+) channels and rho kinase, whereas only the bradykinin response additionally involves the phospholipase A2/cyclooxygenase pathway.

Diabetic plasticity of non-adrenergic non-cholinergic and P2X-mediated rat bladder contractions

We investigated the plasticity effects of diabetes mellitus and diuresis on the non-adrenergic non-cholinergic (NANC) and purinergic (P2X-type) contractile responses in longitudinal rat bladder strips. Female Sprague-Dawley rats received streptozotocin to induce diabetes, or sucrose in water to induce diuresis as a control condition for polyuria. Experiments were carried out at four weeks after treatments, using bladders from non-treated rats as control. Urinary bladder strips were electrically stimulated throughout the experiments to generate neurally evoked contractions (NEC). In all cases, P2X-mediated purinergic contractions were evaluated at the beginning and end of the stimulations with α,β-methylene-adenosine triphosphate (α,βMeATP). The NANC responses were assessed by using two independent protocols. First, cholinergic receptors were activated with carbachol (CCh), followed by inhibition of the muscarinic component with atropine. In the second protocol, the application order for CCh and atropine was reversed. The NANC response, unmasked with the application of atropine, and the P2X purinergic contractions were analyzed. NANC contractions in diabetic bladder strips are more resistant to the desensitizing effects caused by activation of cholinergic receptors. In early stages of experimental diabetes, NANC responses in diabetic strips are less sensitive to functional inhibition mediated by the cholinergic activation. However, P2X-mediated purinergic contractions are more sensitive to desensitization in diabetic or diuretic bladders. For instance preventing muscarinic receptor activation with atropine does not counteract the desensitization of purinergic contractions in either diabetic or diuretic strips. We suggest that diabetes may induce a plasticity of the NANC and P2X-mediated bladder contractile responses. The first one may be associated with diabetic neuropathic damage to bladder nerves, while impaired P2X purinergic contractions might be associated with detrusor hypertrophy observed in diabetic and diuretic strips.

The effects of aqueous extraction Rosmarinus officinalis L. on rat bladder contractions in vitro

Objective. To evaluate the effect of Rosmarinus officinalis L (Labiatae ), an effective and herbal reputed plant for the treatment of urinary ailments, on rat bladder contractilityMethodAnimal experiments were performed in accordance with the national guidelines for use and care of laboratory animals and approved by the local animal care committee of Ataturk University. Urinary bladders were removed from adult male Sprague ‐ Dawley rats. Strips were cut from the bladder body and placed in organ baths containing Krebs solution. The effects of four different doses (150, 300, 600 and 1200 μg/ml) of Rosmarinus officinalis L were investigated on rat bladder contractility induced by 60 mmol/L KCl and 10−4 mol acetylcholine.ResultsContractile tensions were normalized by using the percentage contraction induced by 60 mmol/L KCl and 10−4 mol acetylcholine. The effect of Rosmarinus officinalis L on the urinary bladder contractility induced Ach and KCl. There is no statistical difference between groups (n=6, P>;0.05)ConclusionAny effect of Rosmarinus officinalis L was not observed on the contractions of the urinary bladder of rat that are induced by both Ach and KCl. It can be expressed that Rosmarinus officinalis L which is used in the herbal treatment of some urinary disease does not affect the activity of smooth muscles of urinary bladder.This study was supported by Ataturk University Research Foundation

Oxidative effect ferumoxytol and iron dextran on urinary bladder contraction and impact of antioxidants

IntroductionIntravenous (IV) iron compounds enjoy widespread clinical use. No studies have examined the effect of antioxidants on oxidative damage-associated changes in bladder contractility from IV iron compounds. ObjectiveTo determine if oxidative stress from 2 IV iron compounds effect rat bladder contraction and if coadministered antioxidants are protective. MethodsThree groups of 6 SD rats were studied. Group 1 received weekly 1 mg/kg doses of ferumoxytol (FX) or iron dextran (ID) for 5 doses. Group 2 received coenzyme Q10 (5 mg/kg) plus alpha lipoic acid (10 mg/kg) daily for 4 weeks before starting IV iron, then 1 mg/kg of the 2 iron compounds weekly for 5 doses. Antioxidant treatment continued until the last iron dose. Group 3 were controls and received saline and half received the antioxidants over the same time period. Seven days after the last iron dose, liver and heart samples were analyzed for nitrotyrosine (NT) and dinitrophenol (DNP) content. The contractile responses of bladder strips to field stimulation (FS) (2, 8, and 32 Hz), carbachol (10 μg), and KCl (120 mM) were determined. ResultsDNP concentrations in heart and liver after treatment with FX were similar to control. NT concentrations in both tissues were increased above control with FX. DNP and NT concentrations of both tissues due to ID were higher than both controls and FX. FX had no effect on bladder contractile responses to any form of stimulation, but ID produced decreases in bladder responses to all stimuli. Antioxidants had no effect on bladder contractility in FX-treated rats, but contractile responses to all forms of stimulation were increased by the antioxidants in ID-treated rats. The antioxidants had no effect on control rats. ConclusionFX and ID caused oxidative stress to several organs, but FX was less stressful than ID. Antioxidants attenuated the effects of ID on bladder contractility.

24 EFFECTS OF MIRABEGRON, A β3-ADRENOCEPTOR AGONIST, ON THE PRIMARY BLADDER AFFERENT ACTIVITY SYNCHRONIZED WITH RHYTHMIC BLADDER CONTRACTIONS IN RATS IN COMPARISON WITH THOSE OF OXYBUTYNIN

You have accessJournal of UrologyUrodynamics/Incontinence/Female Urology: Basic Research (1)1 Apr 201324 EFFECTS OF MIRABEGRON, A β3-ADRENOCEPTOR AGONIST, ON THE PRIMARY BLADDER AFFERENT ACTIVITY SYNCHRONIZED WITH RHYTHMIC BLADDER CONTRACTIONS IN RATS IN COMPARISON WITH THOSE OF OXYBUTYNIN Naoki Aizawa, Yukio Homma, and Yasuhiko Igawa Naoki AizawaNaoki Aizawa Tokyo, Japan More articles by this author , Yukio HommaYukio Homma Tokyo, Japan More articles by this author , and Yasuhiko IgawaYasuhiko Igawa Tokyo, Japan More articles by this author View All Author Informationhttps://doi.org/10.1016/j.juro.2013.02.1399AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookTwitterLinked InEmail INTRODUCTION AND OBJECTIVES β3-adrenoceptor (β3-AR) agonists can inhibit the single unit mechanosensitve bladder afferent activities (SAAs) in response to bladder distension. These SAAs, however, might be enhanced also by bladder contractions. Therefore, we measured SAAs during rhythmic bladder contractions (RBCs) in an isovolumetric condition, and examined whether mirabegron, a β3-AR agonist, can affect the SAAs in such condition in rats, and compared with the effect of oxybutynin, an antimuscarinic agent. METHODS Twenty-five female SD rats were used. Under urethane anesthesia, SAAs were dissected from the left L6 dorsal roots and identified by electrical stimulation of the left pelvic nerve and by bladder distension. Nerves were classified as an Aδ- or C-fiber by conduction velocity (2.5 m/second). To produce the RBCs, right L6 dorsal roots were kept intact and the urethral meatus was clamped. When RBCs were reproducibly induced by intravesical saline-instillation, the instillation was stopped and the bladder was kept under an isovolumetric condition. Then, vehicle and 1 mg/kg of mirabegron or oxybutynin were administrated intravenously. RESULTS After mirabegron-treatment, the amplitude and duration of RBCs significantly decreased. Similar effects were observed also after oxybutynin-treatment. The interval of RBCs increased and the basal pressure decreased significantly only after mirabegron-treatment. Forty-one single afferent fibers (Aδ-fibers: n=19, C-fibers: n=22) were isolated. SAAs of both Aδ- and C-fibers were enhanced in a fashion synchronized with RBCs. After mirabegron-treatment, the peak of FR (firing rate) of SAAs synchronized with RBCs significantly decreased in Aδ-fibers, but not C-fibers (figure). After oxybutynin-treatment, the peak of FR of both fiber-SAAs significantly decreased, but the change was not significant when the value was normalized by the change in the amplitude of RBCs. CONCLUSIONS The present results indicate that the stimulation of β3-AR by mirabegron can inhibit mechanosensitive primary bladder afferent activities synchronized with RBCs, mainly of Aδ-fibers. However, these effects were not observed with oxybutynin. © 2013 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 189Issue 4SApril 2013Page: e9-e10 Advertisement Copyright & Permissions© 2013 by American Urological Association Education and Research, Inc.MetricsAuthor Information Naoki Aizawa Tokyo, Japan More articles by this author Yukio Homma Tokyo, Japan More articles by this author Yasuhiko Igawa Tokyo, Japan More articles by this author Expand All Advertisement Advertisement PDF downloadLoading ...

Naftopidil inhibits 5-hydroxytryptamine-induced bladder contraction in rats

Naftopidil is an α1D and α1A subtype-selective α1-adrenoceptor antagonist that has been used to treat lower urinary tract symptoms of benign prostatic hyperplasia. In this study, we investigated the effects of naftopidil on 5-hydroxytryptamine (5-HT)-induced rat bladder contraction (10−8–10−4M). Naftopidil (0.3, 1, and 3μM) inhibited 5-HT-induced bladder contraction in a concentration-dependent manner. On the other hand, other α1-adrenoceptor antagonists, tamsulosin, silodosin or prazosin, did not inhibit 5-HT-induced bladder contraction. The 5-HT-induced bladder contraction was inhibited by both ketanserin and 4-(4-fluoronaphthalen-1-yl)-6-propan-2-ylpyrimidin-2-amine (RS127445), serotonin 5-HT2A and 5-HT2B receptor antagonists, respectively. In addition, 1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane (DOI) and α-methyl-5-HT, 5-HT2A and 5-HT2 receptor agonists, respectively, induced bladder contraction. The 5-HT-induced bladder contraction was not inhibited by N-[2-[4-(2-methoxyphenyl)piperazin-1-yl]ethyl]-N-pyridin-2-yl-cyclohexanecarboxamide (WAY-100635), [1-[2[(methylsulfonyl)amino]ethyl]-4-piperidinyl]methyl-1-methyl-1H-indole-3-carboxylate (GR113808) or (R)-3-[2-[2-(4-methylpiperidin-1-yl)ethyl]pyrrolidine-1-sulphonyl]phenol (SB269970), 5-HT1A, 5-HT4 and 5-HT7 receptor antagonists, respectively. Naftopidil inhibited both the 5-HT2A and 5-HT2 receptor agonists-induced bladder contractions. Naftopidil binds to the human 5-HT2A and 5-HT2B receptors with pKi values of 6.55 and 7.82, respectively. These results suggest that naftopidil inhibits 5-HT-induced bladder contraction via blockade of the 5-HT2A and 5-HT2B receptors in rats. Furthermore, 5-HT-induced bladder contraction was enhanced in bladder strips obtained from bladder outlet obstructed rats, with this contraction inhibited by naftopidil. The beneficial effects of naftopidil on storage symptoms such as urinary frequency and nocturia in patients with benign prostatic hyperplasia may be due, in part, to the blockade of the 5-HT2A and 5-HT2B receptors in the bladder.

Distribution and function of the endocannabinoid system in the rat and human bladder

Our aim was to compare expression and distribution of cannabinoid receptors CB1 and CB2, transient receptor potential vanilloid receptor 1 (TRPV1), and modulating enzymes in human and rat bladder. We also evaluated effects of cannabinoid agonists (ACEA, agonist of CB1; GP1A, agonist of CB2) on contractile responses of rat bladder strips. Distribution and expression of CB1, CB2 and TRPV1 receptors and enzymes fatty acid amide hydrolase (FAAH) and N-acyl phosphatidylethanolamine-hydrolyzing phospholipase D (NAPE-PLD) was studied using immunohistochemistry and immunoblotting on human and Wistar rat bladders. The effects of cannabinoid agonists on contractile responses of isolated rat bladder strips to electrical-field stimulation (EFS) or carbachol-evoked responses were determined. Immunoreactivity for CB1 and TRPV1 receptors and FAAH and NAPE-PLD was present in the bladder of both species. CB1 proteins were of different sizes in rat (57 kDa) and human (40 kDa) bladder. CB2 (45 kDa in both species) immunolocalised to both urothelium and detrusor muscle in human bladder but only to detrusor muscle in rat. FAAH proteins were found at 55 kDa for both species. Rat NAPE-PLD protein (44 kDa) was similar in size to that in human bladder (45 kDa). TRPV1 proteins were found at 104 kDa in both species. ACEA (10(-4) M) attenuated bladder contractions by 35 ± 5.4 % (p < 0.001); GP1a had no effect despite the EC50 values for the carbachol dose-response curves for both agonists being significantly shifted to the right. The endocannabinoid system is functionally expressed in both species, with CB1 receptors showing both pre- and postsynaptic inhibitory effects on rat bladder contraction, whereas CB2 acts only postsynaptically.

Effect of Chemical Stimulation of the Medial Frontal Lobe on the Micturition Reflex in Rats

We assessed the influence of the medial frontal lobe on micturition after chemical stimulation. We also examined the relation between the medial frontal lobe and the rostral pontine reticular formation, which has a strong inhibitory effect on micturition. A total of 35 female rats underwent continuous cystometry. Bladder activity changes were examined after physiological saline, glutamate, the glutamate receptor antagonist MK-801, noradrenaline or the adrenergic α-1 receptor antagonist naftopidil was injected in the medial frontal lobe. When glutamate was injected in the medial frontal lobe, MK-801 was also injected in the rostral pontine reticular formation. Glutamate injection in the medial frontal lobe prolonged the interval between bladder contractions while injection of the glutamate antagonist MK-801 shortened the interval. Glutamate injection in the medial frontal lobe just after MK-801 injection in the ipsilateral rostral pontine reticular formation also prolonged the interval between bladder contractions. However, after prior injection of MK-801 in the bilateral rostral pontine reticular formation glutamate injection in the medial frontal lobe did not influence cystometric parameters. Noradrenaline injection in the medial frontal lobe shortened the interval between bladder contractions while injection of its antagonist naftopidil prolonged the interval. Medial frontal lobe neurons excited by glutamate inhibited the micturition reflex via activation of the rostral pontine reticular formation by glutamatergic projection while medial frontal lobe neurons excited by noradrenaline facilitated the micturition reflex. Thus, the medial frontal lobe may be an important integration center for the initiation of micturition and urine storage mechanisms.

Plasticity of non-adrenergic non-cholinergic bladder contractions in rats after chronic spinal cord injury

The purpose of this study was to examine the pharmacologic plasticity of cholinergic, non-adrenergic non-cholinergic (NANC), and purinergic contractions in neurogenic bladder strips from spinal cord injured (SCI) rats. Bladder strips were harvested from female rats three to four weeks after T9–T10 spinal cord transection. The strips were electrically stimulated using two experimental protocols to compare the contribution of muscarinic and NANC/purinergic contractions in the presence and the absence of carbachol or muscarine. The endpoints of the study were: (1) percent NANC contraction that was unmasked by the muscarinic antagonist 4-DAMP, and (2) P2X purinergic contraction that was evoked by α,β-methylene ATP. NANC contraction accounted for 78.5% of the neurally evoked contraction in SCI bladders. When SCI bladder strips were treated with carbachol (10μM) prior to 4-DAMP (500nM), the percent NANC contraction decreased dramatically to only 13.1% of the neurally evoked contraction (P=0.041). This was accompanied by a substantial decrease in α,β-methylene ATP evoked P2X contraction, and desensitization of purinergic receptors (the ratio of subsequent over initial P2X contraction decreased from 97.2% to 42.1%, P=0.0017). Sequential activation of the cholinergic receptors with carbachol (or with muscarine in neurally intact bladders) and unmasking of the NANC response with 4-DAMP switched the neurally evoked bladder contraction from predominantly NANC to predominantly cholinergic. We conclude that activation of muscarinic receptors (with carbachol or muscarine) blocks NANC and purinergic contractions in neurally intact or in SCI rat bladders. The carbachol-induced inhibition of the NANC contraction is expressed more in SCI bladders compared to neurally intact bladders. Along with receptor plasticity, this change in bladder function may involve P2X-independent mechanisms.

Effects of periurethral neuromuscular electrical stimulation on the voiding frequency in rats

This study aims to test the hypothesis that a urethra-to-bladder inhibitory pathway exists through which periurethral neuromuscular electrical stimulation (NMES) inhibits overactive bladder contractions in rats. Bladder overactivity was induced in 22 female Sprague Dawley rats by injection of ketamine/xylazine/acepromizine (K/X/A). A bipolar electrode was placed surgically in the periurethral region to deliver NMES. Intravesical pressure, bladder inter-contraction interval (ICI) and voided volume (VV) were monitored while the bladder was continuously infused with saline. K/X/A induced more frequent bladder contractions (ICI = 48.6 +/- 20.1 s, before cutting the pubo-symphasis) compared to a 10-min ICI induced by urethane. NMES significantly increased ICI (63.1 +/- 31.3 s before vs. 97.2 +/- 42.9 s after NMES, p < 0.001) and VV (0.063 = 0.041 ml before vs. 0.088 = 0.044 ml after NMES, p < 0.02). Injection of K/X/A may potentially be used as a model of bladder overactivity. NMES inhibits bladder contractions in rats with bladder overactivity, which supports the existence of a urethra-to-bladder inhibitory pathway.

Pharmacological effects of propiverine and its active metabolite, M‐1, on isolated human urinary bladder smooth muscle, and on bladder contraction in rats

To investigate the effects of M-1, a major active metabolite of propiverine on the bladder. We have evaluated the effects of M-1 on the contractions induced by carbachol, KCl, CaCl(2), and electrical field stimulation (EFS) in human detrusor smooth muscles, and pelvic nerve stimulation-induced bladder contractions in rats. The effects of M-1 were also compared with the effects of propiverine and tolterodine. Pretreatment with propiverine and tolterodine caused parallel shifts to the right of the concentration-response curves to carbachol. M-1 caused concentration-dependent reduction in the maximum contractile responses induced by carbachol. Although tolterodine did not inhibit the KCl- and CaCl(2)-induced contractions, M-1 and propiverine significantly inhibited these contractions. In the presence of atropine, M-1 and propiverine significantly inhibited the atropine resistant part of the contraction induced by EFS. On the other hand, tolterodine did not have significant inhibitory effects on atropine resistant contractions. Pelvic nerve stimulation induced bimodal phasic and tonic contractions in the rat bladder. M-1 mainly inhibited the phasic contraction. Tolterodine caused a significant inhibition in the tonic contraction, and propiverine had inhibitory effects on both contractions. The present results suggest that M-1 has inhibitory effects on the bladder smooth muscles through calcium antagonistic action. It is possible that the clinical effects of propiverine on the human bladder are based not only on the action of propiverine itself but also on one of its active metabolites, M-1.

Does Phospholipase C Mediate Muscarinic Receptor-Induced Rat Urinary Bladder Contraction?

Muscarinic acetylcholine receptors, particularly M(3) receptors, are physiologically the most important mechanism to induced urinary bladder smooth muscle contraction. Their prototypical signaling response is a stimulation of phospholipase C (PLC), and this also has been shown in the urinary bladder. Nevertheless, it has remained controversial whether PLC signaling mediates bladder contraction induced by muscarinic receptor agonists. Studies in favor and against a role for PLC differed in their experimental protocol (single versus repeated concentration-response curves within a single preparation) and in the PLC inhibitors that have been used. We have now tested whether previous differential conclusions regarding a role for PLC are related to inhibitors and/or experimental protocols. In a single curve protocol, U-73,122 [1-[6-[((17beta)-3-methoxyestra-1,3,5[10]-trien-17-yl)amino]hexyl]-1H-pyrrole-2,5-dione] did not attenuate carbachol responses. In a repeated curve protocol, ET-18-OCH(3) (1-O-octadecyl-2-O-methyl-sn-glycero-3-phosphorylcholine) lacked significant inhibition relative to vehicle time controls. In contrast, D609 (O-tricyclo[5.2.1.02,6]dec-9-yl dithiocarbonate potassium salt) depressed maximal carbachol effects but also nonspecifically inhibited contraction induced by KCl. Neomycin did not affect the carbachol-induced rat urinary bladder contraction. We conclude that previously reported differences relate to the use of inhibitors rather than experimental protocols and that the overall data do not support a role for PLC in M(3) muscarinic receptor-mediated rat bladder contraction.