Vanilloid receptor subtype 1 (VR1) was cloned as a capsaicin receptor from neuronal cells of dorsal root ganglia. VR1 was subsequently round in a few non-neuronal tissues, including skeletal muscle [Onozawa et al., Tissue distribution of capsaicin receptor in the various organs of rats, Proc. Jpn. Acad. Ser. B 76 (2000) 68-72]. We confirmed the expression of VR1 in muscle cells using the RT-PCR method and Western blot analysis, Immunostaining studies with a confocal microscope and an electron microscope indicated that VR1 was present in the sarcoplasmic reticulum (SR), it store or Ca2+. The SR releases Ca2+ to cause a contraction when a muscle is excited. However, SR still releases a small amount of Ca2+ under relaxed conditions, We round that this leakage was enhanced by capsaicin and was antagonized by capsazepine, it capsaicin blocker. indicating that leakage of Ca2+ occurs through a channel composed of VR1. (c) 2005 Elsevier Inc. All rights reserved.