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.