TRP channels are a large family (about 28 genes) of plasma membrane, non-selective cationic channels that are either specifically or ubiquitously expressed in excitable and non-excitable cells.1 According to IUPHAR the TRP family comprises of three main subfamilies on the basis of sequence homology; TRPC, TRPM and TRPV (to date, three extra subfamilies are considered to belong to the TRP family; the TRPA, TRPML, and TRPP).The TRPV subfamily consists of six members, TRPV1-6.TRPV4 (also named OTRPC4) is activated under hypotonic conditions and serves as an osmoreceptor. TRPV4 is expressed in brain, liver, kidney, heart, testis and salivary gland. ATTO dyes are characterized by strong absorption (high extinction coefficient), high fluorescence quantum yield, and high photo-stability. The ATTO-550 fluorescent label is related to the well known dye Rhodamine 6G and can be used with filters typically used to detect Rhodamine.