抄録
TRPV4 is one of the member of themo-TRP channels. We screened brain-TRPV4 mRNA expressions by in situ hybridization, and found hippocampus strongly expressed TRPV4 in addition to choloid plexus, where TRPV4 expression has been reported. We speculated that TRPV4 might be an important ion channel to regulate hippocampal functions. Therefore, we established a new dissociated neural culture system from neonatal mice hippocampi. TRPV4 protein was localized in soma and dendrites in the culture. We also examined whether functional-TRPV4 was expressed in hippocampal neurons by a Ca2+ imaging method with Fura2. The hippocampal neurons responded to the all reported stimulus, such as heat (>32 °C), hypotonic stimulus and 4αPDD, but no response was observed in the TRPV4-mutant neurons. We considered that body temperature activates brain-TRPV4, and the activation might contribute to slight depolarization of the resting membrane potential (RMP). Next, we compared the RMP between wild type and TRPV4-mutant neurons at 37 °C, and found the wild type RMP was approximately 5 mV higher than the TRPV4-mutant RMP. We also performed current-injection experiments in both neurons, and found that TRPV4-mutant neurons required much bigger currents to get their firing. We conclude that TRPV4 is activated by body temperature in hippocampus, and produces proper environments for their firing. [J Physiol Sci. 2006;56 Suppl:S83]
