Effect of duloxetine, a norepinephrine and serotonin reuptake inhibitor, on sneeze-induced urethral continence reflex in rats

Citalopram improves vasomotor syndrome and urogenital syndrome of menopause in Mexican women: a randomized clinical trial

PURPOSE

This study aimed to determine the efficacy of non-hormonal therapy with citalopram vs fluoxetine for treating vasomotor syndrome (VMS) and urogenital syndrome of menopause (GSM) in Mexican women.

METHODS

A parallel prospective randomized clinical trial was conducted in 91 postmenopausal women with a total score on the Menopause Rating Scale (MRS) ≥ 17 and with the clinical diagnosis of VSM and GSM. Patients were randomly assigned to receive citalopram (n = 49) or fluoxetine (n = 42). Follow-up was carried out at 3 and 6 months.

RESULTS

The citalopram group experienced a significant improvement compared to the fluoxetine group in the MRS total score (p < 0.01), as well as in the psychological (p < 0.001) and somatic (p < 0.0001) domains at 3 and 6 months of follow-up. After 6 months of follow-up, the group that received citalopram decreased the relative risk (RR) to present VMS symptoms (RR = 0.30, CI 0.19-0.5, p = 0.0001), depressed mood (RR = 0.31, CI 0.15-0.6, p = 0.0002), irritability (RR = 0.40, CI 0.22-0.73, p = 0.002), anxiety (RR = 0.30, CI 0.13-0.69, p = 0.003), physical and mental exhaustion (RR = 0.35, CI 0.18-0.67, p = 0.001), sexual problems (RR = 0.18, CI 0.06-0.48, p = 0.0001), vaginal dryness (RR = 0.34, CI 0.14-0.80, p = 0.01), and urinary problems (RR = 0.36, CI 0.14-0.92, p = 0.043).

CONCLUSION

We conclude that citalopram tends to improve VSM and GSM symptoms in postmenopausal Mexican women. Thus, we recommend the daily use of citalopram 20 mg. However, further studies will be required to support the results of the present work. These should include a larger number of patients and a placebo group.

CLINICAL TRIAL REGISTRATION

This clinical trial was retrospectively registered by the United States National Library of Medicine in the www.

CLINICALTRIALS

gov database on 04/20/2022. The given test Registration Number is NCT05346445.

Increasing Effects of Selective 5-Hydroxytryptamine Type 2C Receptor Stimulation on Evoked Momentary Urethral Closure in Female Rats and Humans

Under healthy conditions, more than one urethra-closing reflex, including both bladder afferent-independent and -dependent actions, function during momentary elevation of intravesical (bladder) pressure to prevent urinary incontinence. In the current study, the effects of a novel selective 5-hydroxytryptamine type 2C (5-HT2C) receptor agonist, TAK-233, on evoked momentary urethra-closing functions were investigated in female rats and humans to elucidate 5-HT2C receptor functions. In anesthetized female rats, TAK-233 dose-dependently and significantly increased urethral resistance during sneezing in rats with distended vaginas and bilaterally transected pelvic nerves. The drug also dose-dependently and significantly increased urethral resistance during momentary intravesical pressure elevation by electrical stimulation of abdominal muscles in rats with a transected spinal cord at the T8-T9 level and intact pelvic nerves. The increased effects observed during electrical stimulation were abolished by either an intravenously administered selective 5-HT2C receptor antagonist, SB 242084, or bilateral transection of the pelvic nerves or somatic nerves innervating the external urethral sphincter and pelvic floor muscles. In the spinal cord-transected and pelvic nerve-intact rats, TAK-233 enlarged the urethra-closing responses induced by both passive and abrupt intravesical pressure elevation, measured by a microtip transducer located in the middle urethra. Additionally, the effects of TAK-233 on the stimulus threshold of urethral contractile responses induced by transcranial magnetic stimulation were investigated in healthy female volunteers. The drug dose-dependently and significantly lowered this stimulus threshold, indicating an increased sensitivity of the response. These results demonstrate that 5-HT2C receptor stimulation enhances the evoked momentary urethra-closing functions in both female rats and humans. SIGNIFICANCE STATEMENT: 5-hydroxytryptamine (serotonin) type 2C (5-HT2C) receptor stimulation by TAK-233 enhanced urethral resistance in rats during an evoked momentary event in which the bladder afferent-independent or -dependent reflex functions via striated muscle-mediated mechanisms. The increases in sensitivity of transcranial magnetic stimulation-evoked urethral contractile responses in healthy female subjects indicates that this mechanism also functions in humans. The evoked momentary conditions activating these reflexes provide a suitable model to demonstrate the effects of 5-HT2C receptor stimulation.

Effects of a selective androgen receptor modulator (SARM), GSK2849466A, on stress urinary incontinence and bladder activity in rats with ovariectomy-induced oestrogen deficiency

OBJECTIVES

To report the effect of a selective androgen receptor modulators (SARMs) on the urethral continence mechanisms in a rat model of stress urinary incontinence (SUI) induced by bilateral ovariectomy (OVX).

MATERIALS AND METHODS

Female Sprague-Dawley rats with bilateral OVX were used. Rats were divided into five groups; sham operated, vehicle-treated OVX, low-dose SARM-treated OVX (GSK2849466A: 0.005 mg/kg/day, per os [p.o.]), high-dose SARM-treated OVX (GSK2849466A: 0.03 mg/kg/day, p.o.) and dihydrotestosterone (DHT)-treated OVX (1 mg/kg/day, subcutaneous) groups. After 4 weeks of SARM treatments or 3 weeks of DHT treatment (6 weeks after OVX), rats were subjected to evaluation of the sneeze-induced continence reflex using microtransducer-tipped catheter methods, sneeze-induced leak-point pressure, and continuous cystometry measurements, followed by histological analyses of urethral tissues.

RESULTS

(i) OVX significantly impaired urethral continence function after 6 weeks to induce SUI during sneezing. (ii) Low-dose SARM treatment restored urethral baseline pressure (UBP) without affecting the amplitude of urethral response during sneezing (A-URS), partially reversing OVX-induced SUI during sneezing. (iii) High-dose SARM treatment reversed decreases in both UBP and A-URS, more effectively preventing SUI during sneezing. (iv) DHT treatment only restored A-URS without affecting UBP, partially preventing OVX-induced SUI during sneezing. (v) The high-dose SARM treatment induced hypertrophy of the striated and smooth muscle around the urethra. (vi) SARM treatment did not affect bladder function in sham or OVX rats.

CONCLUSION

Treatment with SARMs could be a more effective modality for the treatment of SUI than DHT, without affecting bladder function, by enhancing smooth- and striated muscle-mediated urethral function under stress conditions such as sneezing.

[Therapeutic new targets for stress urinary incontinence in the central nervous system]

Stress urinary incontinence (SUI) is a common and bothersome problem among middle-aged women. However, there are few useful drugs for SUI. Urethral hypermobility and intrinsic sphincter deficiency are two main causes of SUI. Various animal models of SUI, such as vaginal distention, pudendal nerve injury, or ovariectomy, have been developed to study the pathophysiology of SUI. In addition, we have previously reported that cerebral infarction rats also induce SUI. Leak point pressure measurements are the most commonly used methods to evaluate the urethral dysfunction in SUI animal models. Originally, we have developed microtransducer-tipped catheter measurements of urethral activity during sneezing. Previous or our basic research has clarified potential strategies for pharmacotherapy of SUI in the central nervous system. Therapeutic targets include adrenergic and serotonergic (5-HT) receptors in the spinal cord, which stimulate pudendal nerve innervating the external urethral sphincter and/or sympathetic nerve innervating urethral smooth muscle. Activation of α₁-adrenoceptors, 5-HT_2C, or 5-HT₇ receptors enhances the reflex at the spinal cord level whereas pre- or postsynaptic α₂-adrenoceptors and/or 5-HT_1A receptors inhibit the reflex. We have recently reported that stimulation of the spinal μ-opioid receptors by tramadol also enhances the reflex. Thus, we review the recent advances in basic SUI research and potential targets for pharmacotherapy of SUI in the central nervous system.

A Systematic Review of Efficacy, Safety, and Tolerability of Duloxetine

Duloxetine is a serotonin-norepinephrine reuptake inhibitor approved for the treatment of patients affected by major depressive disorder (MDD), generalized anxiety disorder (GAD), neuropathic pain (NP), fibromyalgia (FMS), and stress incontinence urinary (SUI). These conditions share parallel pathophysiological pathways, and duloxetine treatment might be an effective and safe alternative. Thus, a systematic review was conducted following the 2009 Preferred Reporting Items (PRISMA) recommendations and Joanna Briggs Institute Critical (JBI) Appraisals guidelines. Eighty-five studies focused on efficacy, safety, and tolerability of duloxetine were included in our systematic review. Studies were subdivided by clinical condition and evaluated individually. Thus, 32 studies of MDD, 11 studies of GAD, 19 studies of NP, 9 studies of FMS, and 14 studies of SUI demonstrated that the measured outcomes indicate the suitability of duloxetine in the treatment of these clinical conditions. This systematic review confirms that the dual mechanism of duloxetine benefits the treatment of comorbid clinical conditions, and supports the efficacy, safety, and tolerability of duloxetine in short- and long-term treatments.

Dopaminergic urethral closure mechanisms in a rat model of Parkinson's disease

AIMS

Urinary incontinence is prevalent among patients with Parkinson's disease (PD). In the present study, we investigated urethral functions in a rat model of PD induced by 6-hydroxydopamine injection at their substantia nigra pars compacta as well as the roles of selective agonists/antagonist of dopamine D1- and D2-like receptors in active urethral closure mechanisms.

METHODS

We measured changes in the urethral pressure amplitude during electrical stimulation, urethral baseline pressure, and leak point pressure after intravenous administration of selective agonists or antagonists of the dopamine D1- and D2-like receptors in a rat model of PD.

RESULTS

The mean leak point pressure and the mean active urethral response values were significantly smaller for the untreated PD rat group compared with the control group. In PD model, the active urethral response increased significantly after treatment with the dopamine D1-like receptor agonist, whereas that induced by the dopamine D2-like receptor agonist decreased significantly. The response to the D2-like receptor agonist was suppressed in the PD rat by the dopamine D2-like receptor antagonist.

CONCLUSION

Our results suggest that the active urethral closure mechanisms are significantly impaired when dopamine is depleted. In the PD rat, dopamine D1-like receptor activity on the central nervous system appear to partially compensate for urethral functions negatively impacted by the lack of dopamine, whereas dopamine D2-like receptor activity might exacerbate urinary leakage owing to the negative effect of this activated receptor on urethral pressure under increased intra-abdominal pressure.

Effect of ASP2205 fumarate, a novel 5-HT2C receptor agonist, on urethral closure function in rats

The pharmacological profile of ASP2205 fumarate (ASP2205), a novel 5-HT_2C receptor agonist, was evaluated in vitro and in vivo. ASP2205 showed potent and selective agonistic activity for the human 5-HT_2C receptor, with an EC₅₀ of 0.85 nM in the intracellular Ca²⁺ mobilization assay. Rat 5-HT_2C receptor was also activated by ASP2205 with an EC₅₀ of 2.5 nM. Intraduodenal administration (i.d.) of ASP2205 (0.1-1 mg/kg) significantly elevated the leak point pressure (LPP) in anesthetized rats in a dose-dependent manner. This ASP2205 (0.3 mg/kg i.d.)-induced LPP elevation was inhibited by SB242084 (0.3 mg/kg i.v.), a selective 5-HT_2C receptor antagonist. Urethral closure responses induced by intravesical pressure loading in rats were enhanced by ASP2205 (0.3 mg/kg i.v.), which was abolished by pretreatment with SB242084 (0.3 mg/kg i.v.) and bilateral transection of the pudendal nerve. In contrast, ASP2205 (0.3 mg/kg i.v.) did not change the resting urethral pressure in rats. These results indicate that ASP2205 can enhance the pudendal nerve-mediated urethral closure reflex via the 5-HT_2C receptor, resulting in the prevention of involuntary urine loss.

The Effect of Sneezing on the Reduction of Infarct Volume and the Improvement of Neurological Deficits in Male Rats

Background

Sneezing transiently elevates cerebral blood flow. We speculated that induced sneezing, following embolism would restore arterial flow, thereby diminishing infarct volume and improving neurological deficits.

Materials and Methods

Male rats were subjected to middle cerebral artery occlusion (MCAO) using prepared clots (embolization) and randomized into four equal groups as follows: (1) pre-MCAO-induced sneezing (PRMIS), (2) post-MCAO-induced sneezing (POMIS), and (3) pre- and POMIS (PRPOMIS) and the control group (eight rats per group). In the treatment groups, rats' sneezing episodes were induced before MCAO in PRMIS group or before regaining consciousness from surgical anesthesia in other treatment groups by cutting their whiskers during their anesthesia and subsequently inserted them into the rats' nostrils. Infarct volume was evaluated by 2, 3, 5-triphenyl tetrazolium chloride staining, and neurological deficits and brain edema were assessed by Bederson scale deficit scores 24-h post-MCAO.

Results

The infarct volume and brain edema reduced and neurological deficits improved in the induced sneezing groups as compared with the MCAO control group. Compared to the control group, the highest improvements in the infarct volume and neurological deficits were seen in the PRPOMIS group, and POMIS group showed the most significant differences concerning the results of both ischemic and nonischemic brain edema. The highest protective effect was observed in the central region of the MCA territory.

Conclusions

The reduction in ischemia-induced brain injury, brain edema, and neurological deficits by sneezing suggest that brief episodes of acute hypertension after stroke can increase blood flow to the ischemic area and improve recovery.

Role of the serotonergic system in urethral continence reflexes during sneezing in rats

To clarify the role of serotonin (5-HT) in the prevention of stress urinary incontinence (SUI) during sneezing, we investigated the effect of intraperitoneal application of p-chlorophenylalanine (PCPA; a serotonin synthesis inhibitor) and intravenous application of CP-809101 (a 5-HT_2C agonist) or LP44 (a 5-HT₇ agonist) using female rats, in which the neurally evoked continence reflex during sneezing was examined. Amplitudes of urethral pressure response during sneezing (A-URS), urethral baseline pressure (UBP) at the middle urethra, and sneeze-induced leak point pressure (S-LPP) were measured in normal female adult rats with or without drug administration. PCPA decreased A-URS by 35.1 cmH₂O and UBP by 13.3 cmH₂O compared with normal rats. In PCPA-administrated rats, CP-809101 increased A-URS by 24.1 cmH₂O and UBP by 15.1 cmH₂O, and LP44 also increased A-URS by 20.6 cmH₂O and UBP by 11.4 cmH₂O compared with rats treated with PCPA alone. SUI was observed with S-LPP of 40.1 cmH₂O in PCPA-administrated rats, in which CP-809101 and LP44 increased S-LPP by 28.0 and 15.2 cmH₂O, respectively, compared with rats treated with PCPA alone. The effects of CP-809101 and LP44 were antagonized by SB-242084 (a selective 5-HT_2C antagonist) and SB-269970 (a selective 5-HT₇ antagonist), respectively. These results indicate that activation of 5-HT receptors enhances the active urethral closure reflex during sneezing, at least in part via 5-HT_2C and 5-HT₇ receptors.

TAS-303, a Novel Selective Norepinephrine Reuptake Inhibitor that Increases Urethral Pressure in Rats, Indicating Its Potential as a Therapeutic Agent for Stress Urinary Incontinence

Stress urinary incontinence (SUI) is characterized by involuntary leakage associated with exertion, effort, sneezing, coughing, or lifting. Duloxetine, a serotonin norepinephrine reuptake inhibitor, is approved for the treatment of patients with SUI in some European countries, but not in the United States. There is currently no globally approved pharmacological drug for the treatment of patients with SUI. Therefore, a new pharmacological treatment option is required. TAS-303 [4-piperidinyl 2,2-diphenyl-2-(propoxy-1,1,2,2,3,3,3-day₇ )acetate hydrochloride] is a novel small-molecule selective norepinephrine reuptake inhibitor that displays significant norepinephrine transporter (NET) inhibitory activity toward the serotonin or dopamine transporters. In this report, we describe the pharmacological properties of TAS-303 and its effects on urethral function, using preclinical in vitro and in vivo studies. Radioligand-binding studies showed that TAS-303 selectively and potently inhibited [³H]norepinephrine binding to the human NET. Oral administration of TAS-303 (3 mg/kg) significantly increased norepinephrine levels in the plasma, whereas it did not significantly affect epinephrine, dopamine, and serotonin levels. TAS-303 (0.3, 1, and 3 mg/kg) dose-dependently increased basal urethral pressure in normal rats and leak point pressure in vaginal distention rats, exhibiting a maximal effect comparable to duloxetine. In the forced swimming test, TAS-303 (100 mg/kg) showed no significant effects on immobility time in rats, raising the possibility that this agent would have minimal central nervous system side effects at an effective dose for urethral function. These results demonstrate that TAS-303 has therapeutic potential for the treatment of patients with SUI.

Effects of multiple simulated birth traumas on urethral continence function in rats

Multiple vaginal parities have been reported to be an important risk factor for stress urinary incontinence (SUI). Simulated birth trauma with single vaginal distention (VD) has been used to induce the SUI condition in animals; however, the effect of multiple simulated birth traumas on the urethral continence function has not been well characterized. Therefore, we examined the effects of multiple VDs on urethral functions in vivo and the changes in gene expressions of several molecules in the urethra using female SD rats, which were divided into three groups; sham, VD-1 (single VD), and VD-3 groups (3 times of VDs every 2 wk). Two weeks after the final VD, leak point pressure (LPP) and urethral responses during sneezing were evaluated. Also, changes in mRNA levels of urethral molecules were quantified with RT-PCR.　The VD-1 group did not show any change in LPP with only a tendency of decrease in amplitudes of the urethral responses during sneezing (A-URS); however, the VD-3 group showed a significant decrease in LPP and urethral responses such as baseline urethral pressure and A-URS accompanied with SUI episodes during sneezing. Nicotinic receptor subtypes and transforming growth factor (TGF)-β1 were significantly increased in both VD-1 and VD-3 groups while TNF receptor (TNFR)-1, IL-6, collagens, and matrix metalloproteinases-9 were significantly increased only in the VD-3 group.　These data indicate that rats with multiple simulated birth traumas exhibit profound impairment of the urethral continence function and that these functional changes are associated with those in cytokines, extracellular matrix molecules, and nicotinic receptor subtypes in the urethra.

Design, synthesis, and biological evaluation of a novel series of peripheral-selective noradrenaline reuptake inhibitors-Part 2

Peripherally selective inhibition of noradrenaline reuptake is a novel mechanism for the treatment of stress urinary incontinence to overcome adverse effects associated with central action. Herein, we describe our medicinal chemistry approach to discover peripheral-selective noradrenaline reuptake inhibitors to avert the risk of P-gp-mediated DDI at the blood-brain barrier. We observed that steric shielding of the hydrogen-bond acceptors and donors (HBA and HBD) of compound 1 reduced the multidrug resistance protein 1 (MDR1) efflux ratio; however, the resulting compound 6, a methoxyacetamide derivative, was mainly metabolized by CYP2D6 and CYP2C19 in the in vitro phenotyping study, implying the risk of PK variability based on the genetic polymorphism of the CYPs. Replacement of the hydrogen atom with a deuterium atom in a strategic, metabolically hot spot led to compound 13, which was mainly metabolized by CYP3A4. To our knowledge, this study represents the first report of the effect of deuterium replacement for a major metabolic enzyme. The compound 13, N-{[(6S,7R)-7-(4-chloro-3-fluorophenyl)-1,4-oxazepan-6-yl]methyl}-2-[(2H(3))methyloxy]acetamide hydrochloride, which exhibited peripheral NET selective inhibition at tested doses in rats, increased urethral resistance in a dose-dependent manner.

Serotonin syndrome presenting as surgical emergency: A report of two cases

Serotonin syndrome (SS) is an iatrogenic, drug-induced clinical syndrome caused by serotoninergic hyperstimulation. The diagnosis of SS is easily overlooked as most physicians (up to 85%) are unaware of this syndrome as a clinical entity. Diagnosis is also difficult due to its protean manifestations which can mimic a variety of medical conditions. Herein, we describe two cases of SS, who initially presented to the Surgical Department as surgical emergencies. The first case developed urinary retention after the administration of sertraline. The second case developed features mimicking acute intestinal obstruction. Both cases responded to the removal of offending agents and administration of cyproheptadine. There is a need to increase the awareness of SS among physicians because of the widespread use of serotonergic agents all around the world.

Noradrenergic Mechanisms Controlling Urethral Smooth and Striated Muscle Function in Urethral Continence Reflex in Rats

OBJECTIVES

To investigate the role of noradrenergic pathways in the urethral continence reflex during abdominal compression in rats.

METHODS

Under urethane anesthesia, urethral baseline pressure (UBP) and urethral pressure response (UPR) during momentary abdominal compression using a 100 g weight was measured using a transurethral microtransducer-tipped catheter placed at the middle urethra in Sprague-Dawley female rats. Following intravenous (i.v.) application of hexamethonium or α-bungarotoxin to block urethral smooth or striated muscle function, respectively, the effects of terazosin, an α1 -adrenoceptor (AR) antagonist (0.3 mg/kg, i.v.), medetomidine, an α2 -AR agonist (0.3 mg/kg, i.v.) or nisoxetine, a norepinephrine reuptake inhibitor (1 mg/kg, i.v.) followed by terazosin on UBP and UPR were examined.

RESULTS

After hexamethonium pretreatment, terazosin did not alter UBP or UPR, whereas medetomidine significantly decreased UPR by 28% without UBP changes. Nisoxetine significantly increased UPR by 64%, which was eliminated by terazosin, but UBP was not altered by nisoxetine. After α-bungarotoxin pretreatment, UBP and UPR were significantly decreased by terazosin or medetomidine. Nisoxetine induced significant increases in UBP and UPR by 16 and 15%, respectively, which were antagonized by terazosin.

CONCLUSION

These results suggest that: the baseline activity and reflex contraction of urethral smooth muscle are decreased by α1 -AR inhibition or α2 -AR stimulation; the reflex contraction of urethral striated muscle is decreased by α2 -AR stimulation, but not by α1 -AR inhibition; and nisoxetine increases baseline and reflex activity of smooth muscle in addition to striated muscle reflex activity by α1 -AR stimulation. These findings will be useful to understand nerve-mediated urethral closure mechanisms.

Effects of Duloxetine on Urethral Continence Reflex and Bladder Activity in Rats with Cerebral Infarction

PURPOSE

We investigated the effect of duloxetine, a norepinephrine and serotonin reuptake inhibitor, on the sneeze induced continence reflex and on bladder function in rats with cerebral infarction.

MATERIALS AND METHODS

Using urethane anesthesia the effect of duloxetine (1 mg/kg intravenously) on the amplitude of urethral responses during sneezing as well as urethral baseline pressure at the mid urethra was evaluated in normal female adult rats and cerebral infarction rats. Tilt leak point pressure was also measured. In normal and cerebral infarction rats continuous cystometry was evaluated before and after duloxetine injection.

RESULTS

In cerebral infarction rats urethral baseline pressure was 43% lower than in normal rats but the amplitude of urethral responses during sneezing did not differ in the 2 groups. Duloxetine increased the amplitude of urethral responses during sneezing and urethral baseline pressure by 31% and 21%, respectively, in normal rats but did not affect either in cerebral infarction rats. Also, in cerebral infarction rats leak point pressure was 29% lower compared with normal rats. Duloxetine increased leak point pressure in normal rats but not in cerebral infarction rats. Cerebral infarction reduced intercontraction intervals without affecting the amplitude of bladder contractions compared with normal rats. Duloxetine prolonged intercontraction intervals in cerebral infarction rats but not in normal rats.

CONCLUSIONS

These results suggest that cerebral infarction induces not only bladder overactivity but also stress urinary incontinence, which may account for mixed incontinence in patients with cerebral infarction. After cerebral infarction duloxetine reduced bladder overactivity but failed to enhance active urethral closure mechanisms during sneezing, suggesting that disorganization of the brain network after cerebral infarction might influence the effect of duloxetine on lower urinary tract function.

Neural control of the lower urinary tract

This article summarizes anatomical, neurophysiological, pharmacological, and brain imaging studies in humans and animals that have provided insights into the neural circuitry and neurotransmitter mechanisms controlling the lower urinary tract. The functions of the lower urinary tract to store and periodically eliminate urine are regulated by a complex neural control system in the brain, spinal cord, and peripheral autonomic ganglia that coordinates the activity of smooth and striated muscles of the bladder and urethral outlet. The neural control of micturition is organized as a hierarchical system in which spinal storage mechanisms are in turn regulated by circuitry in the rostral brain stem that initiates reflex voiding. Input from the forebrain triggers voluntary voiding by modulating the brain stem circuitry. Many neural circuits controlling the lower urinary tract exhibit switch-like patterns of activity that turn on and off in an all-or-none manner. The major component of the micturition switching circuit is a spinobulbospinal parasympathetic reflex pathway that has essential connections in the periaqueductal gray and pontine micturition center. A computer model of this circuit that mimics the switching functions of the bladder and urethra at the onset of micturition is described. Micturition occurs involuntarily in infants and young children until the age of 3 to 5 years, after which it is regulated voluntarily. Diseases or injuries of the nervous system in adults can cause the re-emergence of involuntary micturition, leading to urinary incontinence. Neuroplasticity underlying these developmental and pathological changes in voiding function is discussed.

Brain-derived neurotrophic factor in urinary continence and incontinence

Urinary incontinence adversely affects quality of life and results in an increased financial burden for the elderly. Accumulating evidence suggests a connection between neurotrophins, such as brain-derived neurotrophic factor (BDNF), and lower urinary tract function, particularly with regard to normal physiological function and the pathophysiological mechanisms of stress urinary incontinence (SUI) and bladder pain syndrome/interstitial cystitis (BPS/IC). The interaction between BDNF and glutamate receptors affects both bladder and external urethral sphincter function during micturition. Clinical findings indicate reduced BDNF levels in antepartum and postpartum women, potentially correlating with postpartum SUI. Experiments with animal models demonstrate that BDNF is decreased after simulated childbirth injury, thereby impeding the recovery of injured nerves and the restoration of continence. Treatment with exogenous BDNF facilitates neural recovery and the restoration of continence. Serotonin and noradrenaline reuptake inhibitors, used to treat both depression and SUI, result in enhanced BDNF levels. Understanding the neurophysiological roles of BDNF in maintaining normal urinary function and in the pathogenesis of SUI and BPS/IC could lead to future therapies based on these mechanisms.

Effects of phosphodiesterase type 5 inhibitor, tadalafil, on continence reflex in rats

INTRODUCTION AND HYPOTHESIS

Effects of tadalafil, a phosphodiesterase type 5 inhibitor, on the urethral continence reflex induced by sneezing were investigated.

METHODS

The amplitude of urethral pressure responses during sneezing (A-URS) and urethral baseline pressure (UBP) were measured in female rats using a microtransducer-tipped catheter. Sneeze leak-point pressure (S-LPP), defined as the lowest amount of pressure required to induce fluid leakage from the urethral orifice during sneezing, was measured in rats with stress urinary incontinence (SUI) induced by vaginal distension. Values were determined before and after tadalafil administration.

RESULTS

Tadalafil dose dependently and significantly decreased A-URS and S-LPP. At the highest dose tested (6.0 mg/kg), A-URS and S-LPP decreased from 49.7 to 32.3 and from 63.9 to 44.2 cmH2O, respectively, whereas UBP did not significantly change.

CONCLUSIONS

Tadalafil attenuated the sneeze-induced urethral continence reflex by relaxing the striated muscles of the external urethral sphincter.

Roles of the spinal glutamatergic pathway activated through α-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA) receptors and its interactions with spinal noradrenergic and serotonergic pathways in the rat urethral continence mechanisms

AIMS

To investigate the role of the glutamatergic pathway and its relationship to noradrenergic and serotonergic pathways in modulation of the urethral continence reflex during sneezing in rats.

METHODS

In female Sprague-Dawley rats under urethane anesthesia, the effects of an α-amino-3-hydroxy-5-meth-ylisoxazole-4-propionic acid (AMPA) glutamate receptor antagonist, a norepinephrine reuptake inhibitor and a serotonin [5-hydeoxytripitamine (5-HT)]2B/2C agonist on the amplitude of urethral responses during sneezing (AURS), urethral baseline pressure (UBP), and sneeze-induced leak point pressure (S-LPP) were investigated.

RESULTS

Intrathecal application (i.t.) of NBQX disodium salt (an AMPA receptor antagonist) decreased AURS dose-dependently by approximately 60% without affecting UBP and caused stress urinary incontinence (SUI) during sneezing in 60% of normal rats. Nisoxetine (i.t.), a norepinephrine reuptake inhibitor, and mCPP (i.t.), a 5-HT(2B/2C), agonist increased AURS, and NBQX (i.t.) abolished these excitatory effects of nisoxetine (i.t.) and mCPP (i.t.), whereas nisoxetine (i.t.) and mCPP (i.t.) did not enhance AURS in the presence of NBQX (i.t.).

CONCLUSION

These results indicate that the glutamatergic pathway acting through AMPA receptors plays a crucial role on the active urethral closure reflex during sneezing at the spinal level, and noradrenergic and serotonergic pathways modulate the reflex via the spinal glutamatergic system in rats.

Role of serotonin receptors in regulation of contractile activity of urinary bladder in rabbits

OBJECTIVE

To evaluate the role of different serotonin (5-hydroxytryptamine [5-HT]) receptor subtypes on urinary bladder contraction, pharmacologic analysis of electromotor activity (EMA) variation was performed using a rabbit bladder model.

MATERIALS AND METHODS

Measurements of EMA were performed on 3 urinary bladder portions: top, body, and trigone. The experiments were performed on 24 Shinshilla rabbits of both sexes, 5-6 months old, and weighing 2.5-4.0 kg. The bladder was isolated. Noninvasive electrodes were superimposed on the surface of the top, body, and trigone of the bladder. Contact between the electrode tips and the bladder surface was achieved. The bladder EMA was measured using bipolar silver electrodes for extracellular recordings.

RESULTS

The stimulation of the serotoninergic fibers and parasympathetic nerve resulted in increased bladder EMA frequency and amplitude (72% and 25%, respectively). The increase in bladder EMA was prevented by administration of selective inhibitors of serotonin receptor subtypes such as droperidol, spiperone, and sumatriptan. Exogenous serotonin administered to the rabbits after vagus nerve excitation increased the typical EMA of the bladder body smooth muscle.

CONCLUSION

The serotoninergic system has been widely implicated in the control of urinary bladder function. In the present study, we have demonstrated that preganglionic fibers and ganglionic serotoninergic neurons, expressing the 5-HT3 and 5-HT4 receptors, and the effector smooth muscle cells, expressing 5-HT1 and 5-HT2 receptors, are actively involved in the regulation of the bladder contractile activity in rabbits.

Pathophysiology of urinary incontinence in murine models

Urethral closure mechanisms under stress conditions consist of passive urethral closure involving connective tissues, fascia and/or ligaments in the pelvis and active urethral closure mediated by hypogastric, pelvic and pudendal nerves. Furthermore, we have previously reported that the active urethral closure mechanism might be divided into two categories: (i) the central nervous control passing onto Onuf's nucleus under sneezing or coughing; and (ii) the bladder-to-urethral spinal reflex under Valsalva-like stress conditions, such as laughing, exercise or lifting heavy objects. There are over 200 million people worldwide with urinary incontinence, a condition that is associated with a significant social impact and reduced quality of life. Therefore, basic research for urinary continence mechanisms in response to different stress conditions can play an essential role in developing treatments for stress urinary incontinence. It has been clinically shown that the etiology of stress urinary incontinence is divided into urethral hypermobility and intrinsic sphincter deficiency, which could respectively correspond to passive and active urethral closure dysfunction. In this review, we summarize the representative stress urinary incontinence animal models and the methods to measure leak point pressures under stress conditions, and then highlight stress-induced urinary continence mechanisms mediated by active urethral closure mechanisms, as well as future pharmacological treatments of stress urinary incontinence. In addition, we introduce our previous reports including sex differences in urethral closure mechanisms under stress conditions and urethral compensatory mechanisms to maintain urinary continence after pudendal nerve injury in female rats.

Effects of propiverine hydrochloride, an anticholinergic agent, on urethral continence mechanisms and plasma catecholamine concentration in rats

INTRODUCTION AND HYPOTHESIS

Anticholinergics are used to treat overactive bladder. Anticholinergic agents such as propiverine hydrochloride reportedly increase plasma catecholamine levels in rats. It is also known that active urethral closure mechanisms prevents stress urinary incontinence (SUI), which is enhanced by central and peripheral noradrenergic system activation. Therefore, we examined the influence of propiverine hydrochloride on urethral anti-incontinence function in rats.

METHODS

Adult female rats were divided into propiverine and vehicle-treated groups. The propiverine group was given propiverine orally once a day for 2 weeks, after which urethral function and plasma concentrations of catecholamine (dopamine, norepinephrine, epinephrine) were tested.

RESULTS

Urethral baseline pressure measured by a microtransducer-tipped urethral catheter and leak-point pressure during passive intravesical pressure elevation were significantly increased in the propiverine group compared with the vehicle group. Plasma norepinephrine and epinephrine levels in the propiverine group were also significantly increased.

CONCLUSIONS

Propiverine treatment that increases plasma catecholamine levels could contribute to improvement of SUI conditions by increasing urethral resistance.

Adaptations in muscle metabolic regulation require only a small dose of aerobic-based exercise

This study investigated the hypothesis that the duration of aerobic-based cycle exercise would affect the adaptations in substrate and metabolic regulation that occur in vastus lateralis in response to a short-term (10 day) training program. Healthy active but untrained males (n = 7) with a peak aerobic power ([Formula: see text]) of 44.4 ± 1.4 ml kg(-1) min(-1) participated in two different training programs with order randomly assigned (separated by ≥2 weeks). The training programs included exercising at a single intensity designated as light (L) corresponding to 60 % [Formula: see text], for either 30 or 60 min. In response to a standardized task (60 % [Formula: see text]), administered prior to and following each training program, L attenuated the decrease (P < 0.05) in phosphocreatine and the increase (P < 0.05) in free adenosine diphosphate and free adenosine monophosphate but not lactate. These effects were not altered by daily training duration. In the case of muscle glycogen, training for 60 versus 30 min exaggerated the increase (P < 0.05) that occurred, an effect that extended to both rest and exercise concentrations. No changes were observed in [Formula: see text] measured during progressive exercise to fatigue or in [Formula: see text] and RER during submaximal exercise with either training duration. These findings indicate that reductions in metabolic strain, as indicated by a more protected phosphorylation potential, and higher glycogen reserves, can be induced with a training stimulus of light intensity applied for as little as 30 min over 10 days. Our results also indicate that doubling the duration of daily exercise at L although inducing increased muscle glycogen reserves did not result in a greater metabolic adaptation.

Neurophysiology and therapeutic receptor targets for stress urinary incontinence

Stress urinary incontinence is the most common type of urinary incontinence in women. Stress urinary incontinence involves involuntary leakage of urine in response to abdominal pressure caused by activities, such as sneezing and coughing. The condition affects millions of women worldwide, causing physical discomfort as well as social distress and even social isolation. This type of incontinence is often seen in women after middle age and it can be caused by impaired closure mechanisms of the urethra as a result of a weak pelvic floor or poorly supported urethral sphincter (urethral hypermobility) and/or a damaged urethral sphincter system (intrinsic sphincter deficiency). Until recently, stress urinary incontinence has been approached by clinicians as a purely anatomic problem as a result of urethral hypermobility requiring behavioral or surgical therapy. However, intrinsic sphincter deficiency has been reported to be more significantly associated with stress urinary incontinence than urethral hypermobility. Extensive basic and clinical research has enhanced our understanding of the complex neural circuitry regulating normal function of the lower urinary tract, as well as the pathophysiological mechanisms that might underlie the development of stress urinary incontinence and lead to the development of potential novel strategies for pharmacotherapy of stress urinary incontinence. Therapeutic targets include adrenergic and serotonergic receptors in the spinal cord, and adrenergic receptors at the urethral sphincter, which can enhance urethral reflex activity during stress conditions and increase baseline urethral pressure, respectively. This article therefore reviews the recent advances in stress urinary incontinence research and discusses the neurophysiology of urethral continence reflexes, the etiology of stress urinary incontinence and potential targets for pharmacotherapy of stress urinary incontinence.

Models for sensory neurons of dorsal root ganglia and stress urinary incontinence

AIMS

To discuss (1) animal models for investigating bladder afferent pathways from the spinal cord to the brain and (2) animal models of stress urinary incontinence (SUI) with a special emphasis on functional and histopathological characteristics of each model.

METHODS

Literature review of spinal mechanisms of bladder afferent pathways and animal models of SUI.

RESULTS

Electrophysiological studies in the rat using pelvic nerve stimulation and recording of evoked potentials in the periaqueductal gray (PAG) prove to be a valuable tool to examine spinal mechanisms of bladder afferent pathways. Animal models of SUI in the rat include vaginal distention as simulated birth trauma, pudendal nerve crush or transection, urethral sphincter injury by electrocauterization, transabdominal urethrolysis, periurethral botulinum-A toxin injection, and pubo-urethral ligament transection. Functional and histopathological changes in the continence mechanism after injury are different between models.

CONCLUSIONS

Using animal models for sensory neurons, intrathecal and intravenous administration of certain drugs can be tested whether they affect the bladder afferent pathways from the spinal cord to the PAG. Animal models of SUI can serve as a tool to develop new pharmacologic therapies or periurethral injection therapies using stem cell implants.

Strain-dependent urethral response

AIMS

The Sprague-Dawley (SD) rat, an out-bred, all-purpose strain, has served well for lower urinary tract research. However, to test new cellular therapies for conditions such as stress urinary incontinence, an in-bred rat strain with immune tolerance, such as the Lewis rat, may be more useful. The objective of this study was to reveal any differences in lower urinary tract continence mechanisms between the Lewis and SD rat.

METHODS

The contribution of (1) the striated and smooth muscle to the mechanical and functional properties of the urethra in vitro, and (2) the striated sphincter to leak point pressure (LPP) and reflex continence mechanisms in vivo were assessed in normal (control) Lewis and SD rats and in a model of stress urinary incontinence produced by bilateral pudendal nerve transection.

RESULTS

Control, Lewis rats had significantly lower LPP, significantly less fast-twitch skeletal muscle and relied less on the striated sphincter for continence than control, SD rats, as indicated by the failure of neuromuscular blockade with alpha-bungarotoxin to reduce LPP. Nerve transection significantly decreased LPP in the SD rat, but not in the Lewis rat. Although the Lewis urethra contained more smooth muscle than the SD rat, it was less active in vitro as indicated by a low urethral baseline pressure and lack of response to phenylephrine.

CONCLUSIONS

We have observed distinct differences in functional and mechanical properties of the SD and Lewis urethra and have shown that the Lewis rat may not be suitable as a chronic model of SUI via nerve transection.

Role of vasopressin V1A receptor in the urethral closure reflex in rats

An enhanced urethral closure reflex via the spinal cord is related to urethral resistance elevation during increased abdominal pressure. However, with the exception of monoamines, neurotransmitters modulating this reflex are not understood. We investigated whether the vasopressin V1A receptor (V1AR) is involved in the urethral closure reflex in urethane-anesthetized female rats. V1AR mRNA was highly expressed among the vasopressin receptor family in the total RNA purified from lamina IX in the spinal cord L6–S1 segment. In situ hybridization analysis of the spinal L6–S1 segment confirmed that these positive signals from the V1ARs were only detected in lamina IX. Intrathecally injected Arg8-vasopressin (AVP), an endogenous ligand, significantly increased urethral resistance during an intravesical pressure rise, and its effect was blocked by the V1AR antagonist. AVP did not increase urethral resistance in rats in which the pelvic nerves were transected bilaterally. Urethral closure reflex responses to the intravesical pressure rise increased by up to threefold compared with the baseline response after AVP administration in contrast to no increase by vehicle. In addition, intravenously and intrathecally injected V1AR antagonists decreased urethral resistance. These results suggest that V1AR stimulation in the spinal cord enhances the urethral closure reflex response, thereby increasing urethral resistance during an abdominal pressure rise and that V1AR plays a physiological role in preventing urine leakage.

Animal models of stress urinary incontinence

Stress urinary incontinence (SUI) is a common health problem significantly affecting the quality of life of women worldwide. Animal models that simulate SUI enable the assessment of the mechanism of risk factors for SUI in a controlled fashion, including childbirth injuries, and enable preclinical testing of new treatments and therapies for SUI. Animal models that simulate childbirth are presently being utilized to determine the mechanisms of the maternal injuries of childbirth that lead to SUI with the goal of developing prophylactic treatments. Methods of assessing SUI in animals that mimic diagnostic methods used clinically have been developed to evaluate the animal models. Use of these animal models to test innovative treatment strategies has the potential to improve clinical management of SUI. This chapter provides a review of the available animal models of SUI, as well as a review of the methods of assessing SUI in animal models, and potential treatments that have been tested on these models.

Properties of urethral rhabdosphincter motoneurons and their regulation by noradrenaline

The urethral rhabdosphincter (URS), commonly known as the external urethral sphincter, facilitates urinary continence by constricting the urethra. Striated muscle fibres in the urethral rhabdosphincter are innervated by Onuf's nuclei motoneurons in the spinal cord. Although noradrenaline (NA) reuptake inhibitors are shown to increase URS tone preventing urinary leakage in incontinent patients, whether or how NA affects URS motoneurons is unknown. Properties of dye-labelled URS motoneurons were investigated by whole-cell patch-clamp recordings in isolated spinal cord slices prepared from neonatal female rats. As previously shown for adult sphincter motoneurons, neonatal URS motoneurons are more depolarized and possess higher input resistance than other spinal α-motoneurons. These distinct properties make URS motoneurons more excitable than other α-motoneurons. Moreover, bath application of noradrenaline (NA) significantly depolarizes URS motoneurons and in many cases evokes action potentials. NA also significantly increases input resistance and reduces rheobase. These changes are reversed with wash, are largely blocked by the α(1)-adrenoceptor-selective antagonist prazosin, and are mimicked by the α(1)-adrenoceptor-selective agonist phenylephrine. In addition, NA significantly reduces the amplitude of the afterhyperpolarization and increases action potential frequency. Both the increase in action potential frequency and the reduction in afterhyperpolarization are occluded by apamin, a small-conductance calcium-activated potassium (SK(Ca)) channel blocker. In conclusion, NA effectively increases the excitability of URS motoneurons through multiple mechanisms. The NA-induced increase in excitability of urethral rhabdosphincter motoneurons could be a key mechanism by which NA reuptake inhibitors improve stress urinary incontinence.

Neural control of the female urethral and anal rhabdosphincters and pelvic floor muscles

The urethral rhabdosphincter and pelvic floor muscles are important in maintenance of urinary continence and in preventing descent of pelvic organs [i.e., pelvic organ prolapse (POP)]. Despite its clinical importance and complexity, a comprehensive review of neural control of the rhabdosphincter and pelvic floor muscles is lacking. The present review places historical and recent basic science findings on neural control into the context of functional anatomy of the pelvic muscles and their coordination with visceral function and correlates basic science findings with clinical findings when possible. This review briefly describes the striated muscles of the pelvis and then provides details on the peripheral innervation and, in particular, the contributions of the pudendal and levator ani nerves to the function of the various pelvic muscles. The locations and unique phenotypic characteristics of rhabdosphincter motor neurons located in Onuf's nucleus, and levator ani motor neurons located diffusely in the sacral ventral horn, are provided along with the locations and phenotypes of primary afferent neurons that convey sensory information from these muscles. Spinal and supraspinal pathways mediating excitatory and inhibitory inputs to the motor neurons are described; the relative contributions of the nerves to urethral function and their involvement in POP and incontinence are discussed. Finally, a detailed summary of the neurochemical anatomy of Onuf's nucleus and the pharmacological control of the rhabdosphincter are provided.

Alpha2-adrenoceptor blockade potentiates the effect of duloxetine on sneeze induced urethral continence reflex in rats

PURPOSE

Serotonin and norepinephrine reuptake inhibitors such as duloxetine have clinical efficacy for stress urinary incontinence. However, the therapeutic dose of duloxetine is often associated with unwanted side effects. We examined whether combined alpha(2)-adrenoceptor antagonists could decrease the duloxetine dose due to synergistic effects.

MATERIALS AND METHODS

We used normal female rats and rats with stress urinary incontinence induced by vaginal distention. Urethral responses were measured using a microtransducer tipped catheter. We evaluated the effect of low dose duloxetine (0.1 mg/kg), alpha(2)-adrenoceptor antagonists (idazoxan or yohimbine) and sequential administration of drugs on urethral pressure response amplitude during sneezing and urethral baseline pressure. Sneeze induced leak point pressure was also measured.

RESULTS

In normal and vaginally distended rats low dose duloxetine did not alter urethral pressure response amplitude during sneezing but it significantly increased urethral baseline pressure. When low dose duloxetine was co-applied with alpha(2)-adrenoceptor antagonists, urethral pressure response amplitude during sneezing was significantly increased. In all 7 vaginally distended rats leakage was observed during sneezing. After low dose duloxetine administration fluid leakage still occurred during sneezing. However, after low dose duloxetine and idazoxan co-administration fluid leakage disappeared in 2 of 7 rats and sneeze induced leak point pressure was significantly increased in the remaining incontinent rats with vaginal distention.

CONCLUSIONS

Findings support the concept that combination therapy with alpha(2)-adrenoceptor antagonists may be an effective, novel strategy to reinforce the clinical efficacy of serotonin and norepinephrine reuptake inhibitors for stress urinary incontinence.

Neural control of the lower urinary tract: peripheral and spinal mechanisms

This review deals with individual components regulating the neural control of the urinary bladder. This article will focus on factors and processes involved in the two modes of operation of the bladder: storage and elimination. Topics included in this review include: (1) The urothelium and its roles in sensor and transducer functions including interactions with other cell types within the bladder wall ("sensory web"), (2) The location and properties of bladder afferents including factors involved in regulating afferent sensitization, (3) The neural control of the pelvic floor muscle and pharmacology of urethral and anal sphincters (focusing on monoamine pathways), (4) Efferent pathways to the urinary bladder, and (5) Abnormalities in bladder function including mechanisms underlying comorbid disorders associated with bladder pain syndrome and incontinence.

Role of 5-HT1A receptors in control of lower urinary tract function in anesthetized rats

The role of 5-hydroxytryptamine (5-HT) 1A (5-HT1A) receptors in lower urinary tract function was examined in urethane-anesthetized female Sprague-Dawley rats. Bladder pressure and the external urethral sphincter electromyogram (EUS EMG) activity were recorded during continuous-infusion transvesical cystometrograms (TV-CMGs) to allow voiding and during transurethral-CMGs (TU-CMGs) which prevented voiding and allowed recording of isovolumetric bladder contractions. 8-Hydroxy-2-(di-n-propylamino)-tetralin (8-OH-DPAT), a 5-HT1A receptor agonist, decreased volume threshold (VT) for initiating voiding and increased contraction amplitude (CA) during TU-CMGs but decreased CA during TV-CMGs. 8-OH-DPAT prolonged EUS bursting as well as the intrabursting silent periods (SP) during voiding. N-[2-[4-(2-methoxyphenyl)-1- piperazinyl]ethyl]-N-(2-pyridinyl)cyclohexanecarboxamine trihydrochloride (WAY-100635), a 5-HT1A antagonist, increased VT, increased residual volume, markedly decreased voiding efficiency, decreased the amplitude of micturition contractions recorded under isovolumetric conditions, and decreased the SP of EUS bursting. These results indicate that activation of 5-HT1A receptors by endogenous 5-HT lowers the threshold for initiating reflex voiding and promotes voiding function by enhancing the duration of EUS relaxation, which should reduce urethral outlet resistance.

Two kinds of urinary continence reflexes during abrupt elevation of intravesical pressure in rats

Urethral closure mechanisms during abrupt elevation of intravesical pressure (P(ves)) were investigated. During sneezing, the middle urethral closing response was observed and it still remained after opening the abdomen. The middle urethral response was almost completely abolished after bilateral transection of somatic nerves innervating the external urethral sphincter and the pelvic floor muscles, while bilateral transection of both pelvic nerves and hypogastric nerves had no effects. Somatic nerve transection resulted in fluid leakage from the urethral orifice during sneezing. Passive increments of P(ves) for 120 seconds by elevating a saline reservoir connected to the bladder also induced the middle urethral closing response in rats with spinal cord transection at T8-T9. The response was totally abolished by cutting pelvic nerves bilaterally, and partially reduced after bilateral transection of pudendal nerves, nerves to pelvic floor muscles or hypogastric nerves. Electrical stimulation of abdominal muscles (ESAM) for 1 second elevated P(ves) in a stimulus-dependent manner in the spinal cord-transected rats, and the P(ves) rise was almost lost when the abdomen was opened. The P(ves) inducing fluid leakage from the urethral orifice was lowered in rats when pelvic nerves or somatic nerves were cut bilaterally, while transection of bilateral hypogastric nerves showed smaller effects. These results indicate that at least two kinds of urinary continence reflexes close the middle urethra during abrupt elevation of P(ves); one reflex observed during sneeze is preprogrammed so as to close the urethra automatically irrespective of bladder afferent activity, and the other reflex is triggered by bladder afferent excitation. During momentary stress events such as sneezing (<0.15 seconds) and ESAM (1 second), the striated muscles mainly contribute to the urethral closure, while during events for a relatively long period like passive P(ves) elevation for 120 seconds, both striated and smooth muscles are involved in the prevention of stress urinary incontinence.

Role of spinal serotonergic pathways in sneeze-induced urethral continence reflex in rats

To clarify the role of spinal serotonergic mechanisms in preventing stress urinary incontinence (SUI) during sneezing, we investigated the effect of intrathecal (it) application of 8-OH-DPAT (a 5-HT(1A) agonist), mCPP (a 5-HT(2B/2C) agonist), and fluoxetine (a serotonin reuptake inhibitor) using a rat model that can examine the neurally evoked continence reflex during sneezing. Amplitudes of urethral pressure responses during sneezing (A-URS), urethral baseline pressure (UBP) at the midurethra, and sneeze-induced leak point pressure (S-LPP) were measured in normal female adult rats and rats with SUI induced by vaginal distention (VD). In normal rats, 8-OH-DPAT decreased A-URS by 48.9%, whereas mCPP increased A-URS by 33.6%. However, A-URS was not changed after fluoxetine. 8-OH-DPAT, mCPP, or fluoxetine did not alter UBP. The effect of 8-OH-DPAT and mCPP was antagonized by WAY-100635 (it), a selective 5-HT(1A) antagonist, and RS-102221 (it), a selective 5-HT(2C) antagonist, respectively. Fluoxetine in the presence of WAY-100635 did not change either A-URS or UBP, but fluoxetine in the presence of RS-102221 decreased A-URS. In VD rats, S-LPP was decreased by 14.6 cmH2O after 8-OH-DPAT, whereas it was increased by 12.8 cmH2O after mCPP. However, S-LPP was not changed after fluoxetine. These results indicate that activation of 5-HT(2C) receptors enhances the active urethral closure reflex during sneezing at the spinal level, whereas 5-HT(1A) inhibits it and that no apparent changes in the sneeze-induced continence reflex after fluoxetine treatment are due to coactivation of excitatory 5-HT(2C) receptors and inhibitory 5-HT receptors other than the 5-HT(1A) subtype. Thus, activation of excitatory 5-HT receptor subtypes such as 5-HT(2C) could be effective for the treatment of SUI.

Pharmacological properties of 2-((R-5-chloro-4-methoxymethylindan-1-yl)-1H-imidazole (PF-3774076), a novel and selective alpha1A-adrenergic partial agonist, in in vitro and in vivo models of urethral function

2-((R-5-chloro-4-methoxymethyl-indan-1-yl)-1H-imidazole (PF-3774076) is a central nervous system (CNS) penetrant, potent, selective, partial agonist at the human alpha1(A)-adrenoceptor, demonstrating efficacy and selectivity in a range of binding and functional assays. In vivo, PF-3774076 increases peak urethral pressure in anesthetized female dogs in a dose-dependent manner, inducing changes in both the proximal and distal portions of the urethra via a central mechanism of action. The profile of this compound suggests that a CNS penetrant partial agonist at the alpha1(A)-adrenoceptor may offer significant benefit in stress urinary incontinence (SUI). However, despite partial agonism at the alpha1(A)-adrenoceptor and selectivity over alpha1(B)- and alpha1(D)-adrenoceptors, PF-3774076 did not offer the necessary degree of separation over cardiovascular events when assessed in in vivo models of cardiovascular function. This may be due to activation of both peripheral and central alpha1(A)-adrenoceptors. These data indicate that although central, partial alpha1(A)-agonists may offer significant benefit in the treatment of SUI, it may not be possible to achieve the desired level of urethral selectivity over cardiovascular events with this class of agent.

Role of alpha2-adrenoceptors and glutamate mechanisms in the external urethral sphincter continence reflex in rats

PURPOSE

We investigated the role of alpha(2)-adrenoceptors and glutamate mechanisms in the urethral continence reflex in response to abdominal pressure increases.

MATERIALS AND METHODS

Under urethane anesthesia external urethral sphincter electromyogram activity was evaluated in spinal cord transected (T8-T9) female rats during lower abdominal wall compression before and after intravenous application of test drugs. The effects of the N-methyl-D-aspartate glutamate receptor antagonist MK-801 (Sigma) or the alpha(2)-adrenoceptor agonist medetomidine (Tocris Cookson, Ellisville, Missouri) (each 0.03, 0.3 and 3 mg/kg intravenously) on external urethral sphincter activity were examined. A 0.3 mg/kg intravenous dose of the alpha(2)-adrenoceptor antagonist idazoxan (Sigma) was then administered before or after the application of 1 mg/kg MK-801 intravenously. In addition, 0.3 mg/kg idazoxan were administered intravenously following the application of 1 mg/kg of the serotonin/norepinephrine reuptake inhibitor duloxetine (Kemprotec, Middlesbrough, United Kingdom) intravenously.

RESULTS

MK-801 and medetomidine dose dependently decreased external urethral sphincter activity. Idazoxan significantly increased external urethral sphincter activity by 64% but the increase in activity after idazoxan was abolished by MK-801. On the other hand, idazoxan did not reverse the inhibitory effects of MK-801. In addition, idazoxan significantly potentiated the duloxetine effects on external urethral sphincter activity by 120%.

CONCLUSIONS

These results indicate that 1) glutamate is a major excitatory neurotransmitter in the urethral continence reflex response to abdominal pressure increases, 2) alpha(2)-adrenoceptor activation suppresses external urethral sphincter activity, probably via presynaptic inhibition of glutamate release and 3) the effects of serotonin/norepinephrine reuptake inhibitors are enhanced by alpha(2)-adrenoceptor inhibition. Therefore, alpha(2)-adrenoceptor antagonists could be beneficial for treating stress urinary incontinence.