Urethral function and histopathology in aged female rats as a stress urinary incontinence model.

OBJECTIVE: Stress urinary incontinence (SUI) is a common disease condition in elderly women, suggesting that its etiology may be linked to aging. To investigate the hypothesis that urethral dysfunction and histopathological changes are possible contributors to SUI in elderly women, several parameters of urethral function, as well as histological parameters, were compared between young and aged rats. METHODS: Virgin female rats were examined at 3 different ages, namely 3, 12, and 24 months, corresponding to young, middle-aged, and aged rats, respectively. Urethral function was assessed by measuring the leak point pressure (LPP), pudendal nerve stimulation (PNS)-induced elevation in urethral pressure, and phenylephrine-induced increase in urethral perfusion pressure (UPP). Histopathological assessments were performed following hematoxylin and eosin (HE), Masson's trichrome, and immunofluorescence staining of urethral tissue. RESULTS: LPP of aged rats was significantly reduced compared to that of both young and middle-aged rats. PNS-induced elevation in urethral pressure in aged rats was also significantly lower than that in young rats. In contrast, there were no significant differences in the phenylephrine-induced increase in UPP between young and aged rats. Connective tissue area in the external urethral sphincter (EUS) layer was increased in aged rats, whereas the smooth muscle layer was histologically similar to that in young rats. The number of EUS fibers was significantly reduced in aged rats, whereas the cross-sectional area of EUS fibers increased from differed compared with young rats. CONCLUSION: We have demonstrated age-related changes in EUS function and morphology in the rat urethra, which are considered to be etiological risk factors for SUI in humans.

Effects of α1-adrenoceptor antagonists on phenylephrine-induced salivary secretion and intraurethral pressure elevation in anesthetized rats.

α(1)-Adrenoceptor antagonists are widely used for the treatment of voiding dysfunction associated with benign prostatic hyperplasia. Activation of α(1)-adrenoceptors is reported to induce salivary secretion in rats and humans. However, the effects of α(1)-adrenoceptor antagonists on salivary secretion remain unknown. Here, we investigated the effects of the α(1)-adrenoceptor antagonists prazosin, silodosin, tamsulosin and urapidil on phenylephrine-induced salivary secretion and compared the results with the effects on phenylephrine-induced intraurethral pressure (IUP) elevation in anesthetized rats. All antagonists inhibited phenylephrine-induced salivary secretion and IUP elevation in a dose-dependent fashion. Comparison of DR(10) values (the dose required to shift the dose-response curve 10-fold to the right) in both tissues showed that the inhibitory effect of silodosin was significantly more potent in the salivary gland than in the urethra (18-fold), but tamsulosin (2.3-fold), prazosin (1.7-fold) and urapidil (1.1-fold) did not show comparable tissue selectivity. These results suggest that α(1)-adrenoceptor antagonists inhibit not only urethral contraction but also salivary secretion, and that high tissue selectivity for the salivary gland over the urethra as shown by silodosin may contribute to the incidence of dry mouth.

Zolpidem increases bladder capacity and decreases urine excretion in rats.

AIMS: To clarify the effects of zolpidem, a gamma-aminobutyric acid (GABA)(A) receptor agonist, on bladder function, and urine production, we investigated the effects of zolpidem administration on bladder overactivity induced by cerebral infarction (CI) and on urine excretion increased by water overloading in Wistar rats. METHODS: CI was induced by left middle cerebral artery occlusion. The effects on bladder function of zolpidem alone or in combination with the GABA(A) receptor antagonist bicuculline, were then examined in the CI rats using cystometry. The antidiuretic effect of zolpidem was investigated in water-loaded and Brattleboro rats (genetically vasopressin-deficient). Blood samples were collected from water-loaded rats to determine the aldosterone level 1 and 6 hr after zolpidem administration. RESULTS: Zolpidem increased bladder capacity dose-dependently, but had no significant effect on bladder contraction pressure in CI rats. Bicuculline dose-dependently inhibited zolpidem-induced increases in bladder capacity without affecting bladder contraction pressure. Zolpidem dose-dependently decreased the volume of urine excreted in water-loaded and Brattleboro rats. Compared with the control group, zolpidem significantly increased the aldosterone concentration in the plasma of water-loaded rats 1 hr after administration. CONCLUSIONS: Zolpidem increased bladder capacity via a GABAergic mechanism in CI rats, and suppressed urine excretion via a pathway that was not through activation of vasopressin V(2) receptors in water-loaded and Brattleboro rats. These results suggest that zolpidem may improve nocturia via an increase in bladder capacity and a decrease in urine excretion.

Optimization of (4,4-difluoro-1,2,3,4-tetrahydro-5H-1-benzazepine-5-ylidene)acetamide derivatives as arginine vasopressin V2 receptor agonists and discussion of their binding modes.

A series of (4,4-difluoro-1,2,3,4-tetrahydro-5H-1-benzazepine-5-ylidene)acetamide derivatives were optimized to achieve potent agonistic activity, both in vitro and in vivo, for the arginine vasopressin V(2) receptor, resulting in the eventual discovery of compound 1g. Molecular modeling of compound 1g with V(2) receptor was also examined to evaluate the binding mode of this series of compounds.

Synthesis and structure-activity relationships of amide derivatives of (4,4-difluoro-1,2,3,4-tetrahydro-5H-1-benzazepin-5-ylidene)acetic acid as selective arginine vasopressin V2 receptor agonists.

A series of (4,4-difluoro-1,2,3,4-tetrahydro-5H-1-benzazepin-5-ylidene)acetamide derivatives was synthesized, and their structure-activity relationships were examined in order to identify potent and selective arginine vasopressin V(2) receptor agonists. Attempts to substitute other chemical groups in place of the 2-pyridilmethyl moiety of 1a led to the discovery that potent V(2) binding affinity could be obtained with a wide range of functional groups. This structural tolerance allowed for the manipulation of other attributes, such as selectivity against V(1a) receptor affinity or avoidance of the undesirable inhibition of cytochrome P450 (CYP), without losing potent affinity for the V(2) receptor. Some representative compounds obtained in this study were also found to decrease urine volume in awake rats.

Preparation of (4,4-difluoro-1,2,3,4-tetrahydro-5H-1-benzazepin-5-ylidene)acetamide derivatives as novel arginine vasopressin V(2) receptor agonists.

The present work describes the discovery of novel series of (4,4-difluoro-1,2,3,4-tetrahydro-5H-1-benzazepine-5-ylidene)acetamide derivatives as arginine vasopressin (AVP) V(2) receptor agonists. By replacing the amide juncture in YM-35278 with a direct ring connection gave compound 10a, which acts as a V(2) receptor agonist. These studies provided the potent, orally active non-peptidic V(2) receptor agonists 10a and 10j.

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.

Characterization of the pharmacology of YM-198313 on volume-regulated anion channels.

Activation of the volume-regulated anion channels (VRAC) is considered to be involved in arrhythmia, but it has not yet been fully elucidated because of the lack of its high affinitive and selective compounds. A newly synthesized compound, YM-198313 (sodium 4-({[2-(methylthio)benzyl]amino}-5-[(1-phenylethyl)thio]isothiazol-3-olate), strongly inhibited VRAC in HeLa cells with an IC50 of 3.03+/-0.05 microM. However, YM-198313 weakly affected both the Ca2+-activated Cl- channels in HTC cells and the cAMP-activated Cl- channels in T84 cells, demonstrating that this compound is selective for VRAC among Cl- channels. At 10 microM, YM-198313 almost completely (100+/-7.8%) inhibited the VRAC current in guinea pig atrial myocytes. However, at the same concentration, YM-198313 showed little inhibitory effect on the cardiac cation currents in ventricular myocytes. We believe that YM-198313 is a potent and selective VRAC inhibitor, therefore, it should be use to clarify the role VRAC plays in arrhythmia.