Abstract
Transient receptor potential melastatine 8 (TRPM8), a member of TRP cation channel family, is activated by cooling and menthol. TRPM8 is expressed in a subgroup of sensory neurons in the trigeminal ganglia (TG) and the dorsal root ganglia (DRG) and in trigeminal nerve fibers of the tongue. If TRPM8 mediates cooling-induced cold sensation, TRPM8 should be expressed in cutaneous nerve terminals of sensory neurons. However, it has remained unresolved whether TRPM8 is expressed in nerve fibers of skin. Here we investigated the expression of TRPM8 protein in skin of nose, fingers of forelimb and hindlimb and ear of mice by immunohistochemical assay using self-made antibody against TRPM8. Tissues of skin of nose, fingers and ear were isolated. Cryostat sections (20 μm) were obtained and immunohistochemically stained. TRPM8 immunoreactivities were detected in nerve fibers of all of skins explored. These results indicate, for the first time, that TRPM8 protein is surely expressed in peripheral nerve endings at skin, implying that TRPM8 mediates cooling-induced cold sensation. [J Physiol Sci. 2007;57 Suppl:S78]
