JTS-653 blocks afferent nerve firing and attenuates bladder overactivity without affecting normal voiding function.

PURPOSE: We evaluated the role of TRPV1 in bladder overactivity based on afferent nerve firing and urodynamic parameters using the selective TRPV1 antagonist JTS-653. MATERIALS AND METHODS: We evaluated the effects of JTS-653 on the increased pelvic nerve discharge and intravesical pressure induced by intravesical infusion of 100 µM capsaicin in anesthetized rats. The effects of JTS-653 on the urodynamic parameters of bladder overactivity induced by intravesical infusion of 30 nM resiniferatoxin or 0.2% acetic acid, or on normal bladder activity were evaluated by cystometry in conscious rats. The effects of JTS-653 on carbachol induced contraction were investigated using bladder muscle strips. RESULTS: JTS-653 significantly suppressed the capsaicin induced increase in nerve discharge and intravesical pressure. Intravesical infusion of resiniferatoxin or acetic acid decreased the intercontraction interval and voided volume. JTS-653 significantly increased the intercontraction interval and voided volume in rats with resiniferatoxin or acetic acid induced bladder overactivity without affecting maximal voiding pressure. The antimuscarinic agent propiverine significantly decreased maximal voiding pressure but did not affect the intercontraction interval or voided volume in rats with acetic acid induced bladder overactivity. In normal rats JTS-653 showed no significant effects on the intercontraction interval, voided volume or maximal voiding pressure. JTS-653 did not affect carbachol induced contraction of the bladder muscle. CONCLUSIONS: Our findings suggest that TRPV1 is involved in bladder overactivity via afferent nerve activation but it is not associated with normal voiding function. A TRPV1 antagonist would be a useful drug for bladder overactivity with a different pharmacological profile than antimuscarinic agents.

Metal components analysis of metallothionein-III in the brain sections of metallothionein-I and metallothionein-II null mice exposed to mercury vapor with HPLC/ICP-MS.

Mercury vapor is effectively absorbed via inhalation and easily passes through the blood-brain barrier; therefore, mercury poisoning with primarily central nervous system symptoms occurs. Metallothionein (MT) is a cysteine-rich metal-binding protein and plays a protective role in heavy-metal poisoning and it is associated with the metabolism of trace elements. Two MT isoforms, MT-I and MT-II, are expressed coordinately in all mammalian tissues, whereas MT-III is a brain-specific member of the MT family. MT-III binds zinc and copper physiologically and is seemed to have important neurophysiological and neuromodulatory functions. The MT functions and metal components of MTs in the brain after mercury vapor exposure are of much interest; however, until now they have not been fully examined. In this study, the influences of the lack of MT-I and MT-II on mercury accumulation in the brain and the changes of zinc and copper concentrations and metal components of MTs were examined after mercury vapor exposure by using MT-I, II null mice and 129/Sv (wild-type) mice as experimental animals. MT-I, II null mice and wild-type mice were exposed to mercury vapor or an air stream for 2 h and were killed 24 h later. The brain was dissected into the cerebral cortex, the cerebellum, and the hippocampus. The concentrations of mercury in each brain section were determined by cold vapor atomic absorption spectrometry. The concentrations of mercury, copper, and zinc in each brain section were determined by inductively coupled plasma mass spectrometry (ICP-MS). The mercury accumulated in brains after mercury vapor exposure for MT-I, II null mice and wild-type mice. The mercury levels of MT-I, II null mice in each brain section were significantly higher than those of wild-type mice after mercury vapor exposure. A significant change of zinc concentrations with the following mercury vapor exposure for MT-I, II null mice was observed only in the cerebellum analyzed by two-way analysis of variance. As for zinc, the copper concentrations only changed significantly in the cerebellum. Metal components of metal-binding proteins of soluble fractions in the brain sections were analyzed by size-exclusion high-performance liquid chromatography (HPLC) connected with ICP-MS. From the results of HPLC/ICP-MS analyses, it was concluded that the mercury components of MT-III and high molecular weight metal-binding proteins in the cerebellum of MT-I, II null mice were much higher than those of wild-type mice. It was suggested that MT-III is associated with the storage of mercury in conditions lacking MT-I, and MT-II. It was also suggested that the physiological role of MT-III and some kind of high molecular weight proteins might be impaired by exposure to mercury vapor and lack of MT-I and MT-II.