Effect of tamsulosin on bladder blood flow and bladder function in a rat model of bladder over distention/emptying induced bladder overactivity.

PURPOSE: Decreased bladder blood flow was the subject of a recent study as a pathophysiological cause of bladder overactivity. We developed a rat model of bladder over distention/emptying induced bladder overactivity and investigated the effect of the α(1)-adrenoceptor antagonist tamsulosin on bladder blood flow and bladder function in this model. MATERIALS AND METHODS: The bladder was distended with 2 ml saline using anesthesia for 2 hours (over distention) and then emptied. Bladder blood flow was measured using a perfusion imager. Micturition behavior and parameters were observed using a metabolic cage and a cystometry method, respectively, from 2 hours after bladder emptying. After model establishment was confirmed we examined the participation of afferent C-fibers and the effects of tamsulosin in rats pretreated with capsaicin (Sigma-Aldrich®) (125 mg/kg) and tamsulosin (1 µg/kg per hour), respectively, using a metabolic cage. RESULTS: Decreased bladder blood flow was observed upon over distention with partial recovery at emptying. Bladder over distention/emptying increased micturition frequency and decreased mean voided volume in the micturition recording study, and decreased the intercontraction interval and voided volume without affecting micturition pressure, threshold pressure or post-void residual volume in the cystometry study. Capsaicin pretreatment did not affect bladder overactivity. However, 1-week continuous treatment with tamsulosin increased bladder blood flow after bladder emptying, resulting in decreased micturition frequency and increased voided volume. CONCLUSIONS: Bladder over distention/emptying induced bladder blood flow decrease/partial recovery and caused bladder overactivity via a mechanism other than capsaicin sensitive C-fiber activation. Findings in tamsulosin treated rats confirmed the potency of tamsulosin to increase bladder blood flow and ameliorate bladder overactivity.

Effect of tamsulosin on bladder microcirculation in a rat ischemia-reperfusion model, evaluated by pencil lens charge-coupled device microscopy system.

OBJECTIVES: To investigate the effect of tamsulosin hydrochloride on bladder microcirculation in a rat ischemia-reperfusion model using a pencil lens charge-coupled device microscopy system (PLCMS). METHODS: Changes in blood flow through a submucosal capillary of the rat bladder were measured during bladder filling using the PLCMS. One week after starting infusion of either physiological saline or tamsulosin, blood flow in the bladder was halted by bladder overdistention via an infusion of physiological saline. The bladder was then emptied to be reperfused with blood. Changes in blood flow through a submucosal capillary of the bladder during ischemia and reperfusion were measured using a PLCMS, and the data obtained for the control group and tamsulosin group were compared. RESULTS: As the bladder was distended, the velocity of red blood cell flow in a submucosal capillary of the bladder slowed and stopped altogether when the bladder became overdistended. In the control group, capillary blood flow improved over time after release from overdistention but failed to return to the baseline level, demonstrating that reperfusion injury to bladder microcirculation was caused by bladder overdistention and emptying. In the tamsulosin group, capillary blood flow rapidly returned to baseline after release from overdistention. CONCLUSIONS: Using a PLCMS, bladder microcirculation was able to be visualized and quantitatively assessed by measuring the velocity of blood flow in a submucosal capillary of the bladder. Findings from the present study suggest that tamsulosin hydrochloride exerts a protective effect on blood flow in ischemia-reperfusion injury of the bladder.

Effects of tamsulosin on bladder blood flow and bladder function in rats with bladder outlet obstruction.

OBJECTIVES: To investigate the mechanism underlying the ameliorating effect of tamsulosin, an alpha(1)-adrenoceptor antagonist, on storage symptoms associated with benign prostatic hyperplasia, the effects of tamsulosin on bladder blood flow (BBF) and bladder function was evaluated in rats with bladder outlet obstruction (BOO). METHODS: BOO was produced by partial ligature of the proximal urethra, which was maintained for 2 weeks. Tamsulosin was subcutaneously administered via an osmotic pump for 2 weeks immediately after the BOO surgery. The BBF in the sham-operated rats, the control BOO rats, and the tamsulosin-treated BOO rats was measured using the fluoromicrosphere method. Each rat was kept in a metabolic cage for observation of micturition behavior. Expression of the alpha(1)-adrenoceptor subtype mRNA in the vesical artery was measured by reverse transcriptase-polymerase chain reaction. RESULTS: BBF was significantly reduced in BOO rats compared with sham-operated rats, and tamsulosin significantly increased the BBF in BOO rats. Tamsulosin ameliorated the decrease in mean voided volume in BOO rats with bladder masses < 500 mg. Expression of the alpha(1)-adrenoceptor subtype in the vesical artery was alpha(1a)- > alpha(1d)-adrenoceptors; almost no expression was observed of alpha(1b)-adrenoceptors in either sham-operated or BOO rats. CONCLUSIONS: Tamsulosin increased BBF in BOO rats via an antagonistic effect, presumably on the alpha(1A)- and/or alpha(1D)-adrenoceptor in the vesical artery mainly, and improved the decrease in mean voided volume. Therefore, the results of this study suggest that tamsulosin improves bladder overactivity via improvement of BBF.

Effects of intravenously and orally administered solifenacin succinate (YM905) on carbachol-induced intravesical pressure elevation and salivary secretion in mice.

Solifenacin succinate is a novel muscarinic receptor antagonist used for the treatment of overactive bladder (OAB). We investigated the effects of solifenacin by oral and intravenous administration on carbachol (CCh)-induced intravesical pressure (IVP) elevation and compared its efficacy with that on CCh-induced salivary secretion in anesthetized mice. Additionally, we also investigated the change in effects between single and repeated oral administration of solifenacin on CCh-induced IVP elevation. Results showed that intravenous administration of solifenacin dose-dependently inhibited the IVP elevation and salivary secretion. The ratio of bladder response to salivary response (ratio of ID(50) values) was 2.1. Oral administration of solifenacin (0.3-30 mg/kg) also inhibited CCh-induced IVP elevation and salivary secretion. Although inhibition of these responses by solifenacin (10, 30 mg/kg) was comparable at early time points (0.5 and 1 h after administration at 10 mg/kg and 0.5 to 2 h after administration at 30 mg/kg), inhibition of CCh-induced IVP elevation was stronger at later time points (2 to 8 h after administration at 10 mg/kg and 4 to 24 h after administration at 30 mg/kg). No significant difference in ID(50) values for IVP elevation was observed between single and repeated (11 d) oral administration of solifenacin (1-30 mg/kg), suggesting no change in efficacy on chronic administration. In conclusion, intravenous and oral solifenacin inhibits CCh-induced IVP elevation more potently than salivary secretion. These results provide further evidence for the clinical use of solifenacin as a promising therapeutic drug for OAB with a low incidence of dry mouth.

Pharmacological characterization of a new antimuscarinic agent, solifenacin succinate, in comparison with other antimuscarinic agents.

Solifenacin succinate [YM905; (3R)-1-azabicyclo[2.2.2]oct-3-yl(1S)-1-phenyl-3,4-dihydroisoquinoline-2(1H)-carboxylate monosuccinate] is a new muscarinic receptor antagonist developed for the treatment of overactive bladder. The aim of the present study was to evaluate the antimuscarinic properties of solifenacin and to compare the results with those obtained for tolterodine, oxybutynin, darifenacin, propiverine and atropine. In radioligand receptor binding assay, Ki values of solifenacin for human muscarinic M1, M2, M3, M4 and M5 receptors were 26, 170, 12, 110 and 31 nM, respectively. In isolated rat urinary bladder, solifenacin competitively antagonized carbachol-induced contractions, with a pA2 value of 7.44+/-0.09. In these in vitro studies, the antimuscarinic action of solifenacin was more potent than that of propiverine and less potent than those of tolterodine, oxybutynin, darifenacin and atropine. In anesthetized rats, solifenacin and oxybutynin increased the maximum bladder capacity in a dose-dependent manner and also decreased the maximum intravesical pressure. The dosages required to produce a 30% increase in maximum bladder capacity (ED30 values) of solifenacin and oxybutynin were 0.35 and 0.30 mg/kg i.v., respectively, indicating approximately equal efficacies. These results support the fact that solifenacin, similarly to currently used antimuscarinic agents, is an effective agent in the treatment of overactive bladder symptoms such as urinary frequency and urge incontinence.

Effect of antimuscarinic drugs used for overactive bladder on learning in a rat passive avoidance response test.

Antimuscarinic drugs are used for the treatment of overactive bladder. One adverse effect associated with their use, however, is cognitive impairment arising from their anticholinergic action. Here, we examined the effects of antimuscarinic drugs on learning using a passive avoidance task in rats. Drugs were intravenously administered 10 min before an acquisition trial, followed 24 h later by measurement of latency time in the passive avoidance task in a retention trial. Oxybutynin (0.1-1 mg/kg i.v.), propiverine (1-10 mg/kg i.v.) and scopolamine (0.1-1 mg/kg i.v.) impaired learning at doses of 0.3 mg/kg i.v. or more, 10 mg/kg i.v., and 0.3 mg/kg i.v. or more, respectively. Tolterodine (0.1-1 mg/kg i.v.) tended to impair these functions at a dose of 1 mg/kg i.v. In contrast, darifenacin (0.1-1 mg/kg i.v.) and solifenacin (0.3-3 mg/kg i.v.) showed no impairment of these functions. We also examined the effects of antimuscarinic drugs on learning enhanced by the cholinesterase inhibitor donepezil at a dose of 0.1 mg/kg i.v. in scopolamine-treated rats. Oxybutynin (0.1-1 mg/kg i.v.) impaired these donepezil-enhanced functions, whereas solifenacin (0.3-3 mg/kg i.v.) produced no significant impairment. These results suggest that antimuscarinic drugs such as darifenacin, solifenacin and tolterodine may have less effect on cognitive function in the treatment of patients with overactive bladder.

Effect of tamsulosin on spontaneous bladder contraction in conscious rats with bladder outlet obstruction: comparison with effect on intraurethral pressure.

We investigated the effect of tamsulosin, an alpha(1)-adrenoceptor antagonist, on bladder function, especially spontaneous bladder contractions before micturition (premicturition contraction), in conscious rats with bladder outlet obstruction induced by partial urethral ligation, and compared the results with the effect on intraurethral pressure response in anesthetized rats. In obstructed rats, the alpha(1)-adrenoceptor antagonists tamsulosin, naftopidil and urapidil and non-selective alpha-adrenoceptor antagonist phentolamine inhibited premicturition contractions in a dose-dependent fashion. In contrast, yohimbine, an alpha(2)-adrenoceptor antagonist, and atropine, a muscarinic receptor antagonist, hardly inhibited them. Tamsulosin and urapidil showed clearly inhibitory effects on increases in intraurethral pressure induced by phenylephrine, an alpha(1)-adrenoceptor agonist, in the same dose range as that at which they inhibited premicturition contractions, whereas naftopidil required somewhat higher doses to inhibit increases in intraurethral pressure than those at which it inhibited premicturition contractions. In conclusion, premicturition contractions observed in obstructed rats were sensitive to alpha(1)-adrenoceptor antagonists, but not to alpha(2)-adrenoceptor or muscarinic receptor antagonists. Tamsulosin was shown to be effective against both premicturition contraction and intraurethral pressure response in the same dose range in rats. These results partly support the fact that tamsulosin has improved storage symptoms as well as voiding symptoms in patients with lower urinary tract symptoms associated with bladder outlet obstruction by blocking alpha(1)-adrenoceptors.

Participation of endogenous endothelin and ETA receptor in premicturition contractions in rats with bladder outlet obstruction.

A relationship between endogenous endothelins and bladder overactivity has recently been suggested, but the related endothelin receptor subtype has not been identified. Here, to evaluate the involvement of endothelin-1 and its receptors in bladder overactivity, we investigated endothelin-1 levels and the expression of its receptors in the bladder of rats with bladder outlet obstruction (BOO), a model for bladder overactivity. We also investigated the effects of a selective endothelin ET(A) receptor antagonist, (E)-N-[6-methoxy-5-(2-methoxyphenoxy)[2,2'-bipyrimidin]-4-yl]-2-phenylethenesulfonamide monopotassium salt (YM598), on bladder functions in conscious BOO rats. Partial obstruction of the urethra led to a progressive increase in bladder weight from weeks 1 to 6. Binding assays performed using plasma membranes prepared from these bladders to estimate endothelin receptor density from the maximum [(125)I]endothelin-1 binding showed increased endothelin receptor density (about double) at 1, 2, and 6 weeks after the operation in the BOO bladder. The densities of endothelin ET(A) receptors in the bladder of sham-operated and BOO rats at 2 weeks after operation were about 3.5 and 5 times those of endothelin ET(B) receptors respectively. Furthermore, the endothelin-1 level was also increased in the BOO bladder. Two weeks after operation, BOO rats showed an increase in maximum bladder capacity and micturition volume and the generation of premicturition contractions. The frequency of premicturition contractions was dose-dependently reduced by YM598 (0.1-3 mg/kg, i.v.) without any effect on other voiding parameters in BOO rats. These data suggest that endothelin-1 and endothelin ET(A) receptors might be involved in the generation of premicturition contractions in BOO rats, and that endothelin ET(A) receptor antagonists such as YM598 may have ameliorating effects in patients with bladder overactivity associated with BOO.

In vivo studies on the effects of alpha1-adrenoceptor antagonists on pupil diameter and urethral tone in rabbits.

Alpha1-adrenoceptors mediate contraction of iris dilator smooth muscle and hence pupil dilatation. We compared the ability of i.v. bolus injections of alfuzosin, doxazosin, naftopidil, prazosin, tamsulosin and terazosin to antagonise phenylephrine-induced mydriasis relative to their potency for inhibiting phenylephrine-induced elevations of intraurethral pressure (IUP) in rabbits. Moreover, we compared the ability of these drugs to induce miosis in conscious rabbits in the absence of phenylephrine. All antagonists inhibited the effects of phenylephrine on pupil size and IUP, and the ratio of the respective ED50 values was close to unity in all cases. The doses required to induce statistically significant miosis in the absence of phenylephrine were 30- to 100-fold higher than those inhibiting phenylephrine-induced mydriasis for all antagonists, except for naftopidil. Moreover, the miotic effects of all alpha1-adrenoceptor antagonists were fully reversible within 8 h. We conclude that alfuzosin, doxazosin, naftopidil, prazosin, tamsulosin and terazosin inhibit phenylephrine-induced mydriasis in the same dose range as they inhibit elevations in IUP. Higher doses of all antagonists are required to induce miosis in the absence of an exogenous agonist, and such miosis is always reversible within hours.

Endomorphin-2 and endomorphin-1 promote the extracellular amount of accumbal dopamine via nonopioid and mu-opioid receptors, respectively.

Activation of mu-opioid receptors in the nucleus accumbens (NAc) is known to increase accumbal dopamine efflux in rats. Endomorphin-2 (Tyr-Pro-Phe-Phe-NH(2); EM-2) and endomorphin-1 (Tyr-Pro-Trp-Phe-NH(2); EM-1) are suggested to be the endogenous ligands for the mu-opioid receptor. As the ability of EM-2 and EM-1 to alter the accumbal extracellular dopamine level has not yet been studied in freely moving rats, the present study was performed, using a microdialysis technique that allows on-line monitoring of the extracellular dopamine with a temporal resolution of 5 min. A 25 min infusion of either EM-2 or EM-1 into the NAc (5, 25, and 50 nmol) produced a dose-dependent increase of the accumbal dopamine level. The EM-2 (50 nmol)- and EM-1 (25 and 50 nmol)-induced dopamine efflux were abolished by intra-accumbal perfusion of tetrodotoxin (2 muM). Intra-accumbal perfusion of the mu-opioid receptor antagonist CTOP (D-Phe-Cys-Tyr-D-Trp-Orn-Thr-Phe-Thr-NH(2); 3 nmol) failed to affect the EM-2 (50 nmol)-induced dopamine release, whereas it significantly inhibited the EM-1 (25 and 50 nmol)-induced dopamine release. The EM-1 (50 nmol)-induced accumbal dopamine efflux was significantly reduced by the systemic administration of the putative mu1-opioid receptor antagonist naloxonazine (15 mg/kg, intraperitoneally (i.p.), given 24 h before starting the perfusion). Systemic administration of the aspecific opioid receptor antagonist naloxone (1 mg/kg, i.p., given 10 or 20 min before starting the perfusion) also failed to affect the EM-2 (50 nmol)-induced dopamine efflux, whereas it significantly inhibited the EM-1 (25 and 50 nmol)-induced dopamine efflux. The present study shows that the intra-accumbal infusion of EM-2 and EM-1 increases accumbal dopamine efflux by mechanisms that fully differ. It is concluded that the effects of EM-2 are not mediated via opioid receptors in contrast to the effects of EM-1 that are mediated via mu1-opioid receptors in the NAc.

Effects of solifenacin succinate (YM905) on detrusor overactivity in conscious cerebral infarcted rats.

Solifenacin succinate [YM905, (+)-(1S,3'R)-quinuclidin-3'-yl 1-phenyl-1,2,3,4-tetrahydroisoquinoline-2-carboxylate monosuccinate] is a novel muscarinic receptor antagonist. We examined the effects of solifenacin and two other muscarinic receptor antagonists, tolterodine and propiverine, on detrusor overactivity in cerebral infarcted rats. Evaluation was done under conscious conditions using cystometry 1 day after middle cerebral artery occlusion. The cerebral infarcted rats showed decreases in bladder capacity and voided volume and an increase in residual volume, but no change in micturition pressure. Solifenacin increased bladder capacity and voided volume at doses of 0.03 mg/kg i.v. or more. Tolterodine increased bladder capacity and voided volume at 0.03 and 0.1 mg/kg i.v., while propiverine increased bladder capacity and voided volume at 1 mg/kg i.v. and at 0.3 and 1 mg/kg i.v., respectively. In contrast, none of the three drugs affected residual volume or micturition pressure. These results suggest that solifenacin may improve detrusor overactivity without causing urinary retention and may be a promising drug in the treatment of patients with overactive bladder syndrome.

Celecoxib does not induce convulsions nor does it affect GABAA receptor binding activity in the presence of new quinolones in mice.

We sought to determine whether celecoxib would induce convulsions when coadministered with new quinolone antimicrobial agents in mice. The oral administration of celecoxib (500 mg/kg) alone or in combination with enoxacin (500 mg/kg), lomefloxacin (1000 mg/kg), ciprofloxacin (1000 mg/kg), or levofloxacin (1000 mg/kg) induced no convulsions in mice. In contrast, some nonsteroidal anti-inflammatory drugs (NSAIDs), fenbufen (200 mg/kg), indomethacin (500 mg/kg), and naproxen (500 mg/kg) induced convulsions in combination with the majority of the new quinolones tested. gamma-Aminobutyric acid (GABA)(A) receptor blockade-mediated neuronal excitation is assumed to be involved in these toxic convulsions. Enoxacin (100 microM) and lomefloxacin (100 microM) only slightly reduced [3H]muscimol binding to GABA(A) receptors in mouse whole brain membrane. However, these reductions were markedly enhanced by the addition of fenbufen (100 microM), indomethacin (100 microM), or naproxen (100 microM). Conversely, celecoxib (100 microM) had no apparent effect on [3H]muscimol binding when applied alone or in combination with enoxacin or lomefloxacin. These results suggest that celecoxib may be a more desirable anti-inflammatory agent with respect to drug interactions with new quinolones compared with some conventional NSAIDs.

Altered pre- and postsynaptic dopamine receptor functions in spontaneously hypertensive rat: an animal model of attention-deficit hyperactivity disorder.

Dopamine receptor function in spontaneously hypertensive rats (SHR) and in control progenitor Wistar-Kyoto (WKY) rats was assessed from their dopamine D1-like/D2-like receptor-mediated jaw movements and dopamine release from the nucleus accumbens and from the ventrolateral striatum measured by an in vivo microdialysis technique. Spontaneous locomotor activity and rearing were significantly higher in SHR than in WKY rats. Co-administration of SKF 38393 (1.0, 2.0 and 3.0 mg/kg), a dopamine D1-like receptor agonist, and quinpirole (1.0 mg/kg), a dopamine D2-like receptor agonist, produced repetitive jaw movements in WKY rats in a dose-dependent manner. However, this synergism was not evident in SHR. Basal dopamine levels in both the nucleus accumbens and the ventrolateral striatum were lower in SHR than WKY rats, though the levels of dopamine were lower in the nucleus accumbens than the ventrolateral striatum in both strains. After infusion of quinpirole (100 microM for 180 min) the dopamine levels in both regions were reduced. In the nucleus accumbens, the quinpirole-mediated reduction of dopamine release at 40 min and 60 min after infusion was larger in SHR than WKY rats, whereas this difference between the SHR and WKY rats was small in the ventrolateral striatum. The present study therefore suggests that, when compared to WKY rats, postsynaptic dopamine D1-like/D2-like receptors in the SHR are hyposensitive, while presynaptic dopamine D2-like receptors located particularly in the nucleus accumbens are hypersensitive.