The TRPM subfamily consists of 8 members divided in to three major groups: TRPM1/3, TRPM4/5, and TRPM6/7. TRPM2 and TRPM8 are not included in any of the groups since they are quite different even with respect to each other. TRPM3 is alternatively spliced into active variants. TRPM3a1 and TRPM3a2 in mouse are monovalent and divalent-selective channels, respectively. This differential selectivity strongly suggests that their cellular role depends on the relative expression of each variant type. In addition, both splice variants display constitutive outwardly rectifying currents. They somewhat resemble TRPM6 and TRPM7 channels such that their currents are inhibited by intracellular Mg2+ .TRPM3 is highly expressed in the kidney, and to a lesser extent in the brain, testis, and spinal cord.