Takehito Naruoka

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 Onufs 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.

Time-dependent changes in bladder function and plantar sensitivity in a rat model of fibromyalgia syndrome induced by hydrochloric acid injection into the gluteus

What’s known on the subject? and What does the study add?

α2‐Adrenoceptor as a New Target for Stress Urinary Incontinence

Objectives: We examined glutamate and/or α2‐adrenoceptor (AR) mechanisms in the control of external urethral sphincter (EUS) activity in response to stress conditions.

MP17-06 ROLE OF SPINAL α2-ADRENOCEPTORS AND IMIDAZOLINE RECEPTORS IN THE CONTROL OF VOIDING AND CONTINENCE REFLEXES IN CONSCIOUS RATS

and immunocytochemistry, amphotericin-perforated patch-clamp electrophysiology on native freshly-isolated human DSM cells, as well as functional studies on DSM contractility of DSM isolated strips from donor patients, and the novel TRPM4 channel inhibitor 9phenathrol. RESULTS: RT-PCR experiments detected mRNA message for TRPM4 channels in whole DSM tissue and single DSM cells. Western blot analysis and immunohistochemical staining revealed TRPM4 protein expression in whole DSM tissue. Immunocytochemical experiments further detected TRPM4 protein expression in isolated single DSM cells. Voltage-clamp experiments on freshlyisolated native human DSM cells showed that inhibition of TRPM4 channels with 9-phenathrol significantly decreased the transient inward cation currents (TICCs) activity, when recorded at -70 mV. Pretreatment of DSM cells with xestospongin C, an inositol-3phosphate receptor inhibitor, abolished the TICCs. Current-clamp experiments demonstrated that inhibition of TRPM4 channels with 9-phenathrol hyperpolarized DSM cell resting membrane potential by w11 mV. In vitro functional studies on DSM contractility revealed that TRPM4 channel inhibitor 9-phenantrol significantly attenuated the spontaneous phasic, carbachol-induced, and nerve-evoked contractions in human DSM isolated strips in a concentration-dependent manner. CONCLUSIONS: Our results demonstrate the novel finding that TRPM4 channels are expressed in human DSM and support the concept that they regulate human DSM excitability and contractility. Therefore, TRPM4 channels may be considered as novel targets for treatment of overactive bladder.

951 ANALYSIS OF TRANSIENT RECEPTOR POTENTIAL CHANNELS RELATED TO BLADDER OVERACTIVITY INDUECED BY PELVIC ORGAN CROSS-SENSITIZATION IN RATS

INTRODUCTION AND OBJECTIVES: Pelvic organ cross-sensitization has been proposed as one of the pathogenesis of bladder pain syndrome/interstitial cystitis. Thus, we examined changes in bladder function after the stimulation of transient receptor potential (TRP) channels in the colon, uterus or stomach because TRP channels are one of the main nociceptive receptors. METHODS: Under isoflurane anesthesia, a polyethylene catheter was implanted into the colon, uterus or stomach as well as the bladder in female Sprague-Dawley rats, and cystometry was then performed in an awake condition. 1) Capsaicin (TRPV1 activator; 1, 3, 10 & 30mM), R1747 (TRPV4 activator; 1, 3, 10 & 30mM), allyl isothiocyanate (AITC: TRPA1 activator; 1, 3, 10 & 30%) or menthol (TRPM8 activator; 3, 10, 30 & 100%) was cumulatively applied in a 50ul solution of each dose with 30min intervals into the colon, uterus or stomach. 2) Time-dependent changes in bladder function were examined after 30% AITC injection into the colon or uterus. We also examined changes in bladder function when ruthenium red (RR: TRPA1 inhibitor) was intrathecally (i.t.; 0.03ug, 5ul) or intravenously (i.v.; 3mg/kg, 0.5ml/ kg) applied 30min before or 120min after colon AITC injection. RESULTS: 1) There were no significant changes in bladder function after the TRPV1, V4 or M8 stimulation in the colon or uterus, whereas threshold pressure (TP) and intercontraction interval (ICI) were significantly decreased by 10% or greater AITC injection into the colon or 30% AITC injection into the uterus. None of TRP channel stimulations in the stomach influenced bladder function. 2) TP and ICI were significantly decreased from 30 min and 60 min after 30% AITC injection, respectively, in the colon. TP and ICI were significantly decreased 60 min after AITC injection in the uterus, and became stable after 120min. Bladder overactivity induced by colon AITC application was prevented by the pretreatment of RR (i.v. and i.t.). On the other hand, only the i.t., but not i.v., application of RR increased TP and ICI significantly when RR was applied after the induction of colon-toblabber cross-sensitization. CONCLUSIONS: Bladder overacitvity occurs from 30–60 min after the stimulation of TRPA1 channels, but not TRPV1, V4 or M8, in the colon or uterus, indicating the importance of TRPA1 for the pelvic organ cross-sensitization. In addition, central sensitization seems to be involved in the pelvic organ cross-sensitization because i.t. application of a TRPA1 inhibitor can attenuate the colon-to-bladder cross-sensitization.