Fig. 5.

TRPV4-mediated heat-evoked responses are modulated by osmolarity. A, Representative current traces of the second (I), fourth (II), and sixth (III) responses of a TRPV4-expressing oocyte subjected to consecutive heat stimuli (45°C; horizontal open bars). Hypertonic bath solution (410 mOsm; horizontalfilled bar) was applied 1 min before the third heat stimulus, and the oocytes were washed for 2 min after the fourth heat stimulus.Inset, Amplitudes of heat-evoked responses II and III relative to response I in 410 mOsm-treated (open columns) and untreated (filled columns) TRPV4- and TRPV1-expressing oocytes. Data represent the mean ± SEM of four oocytes. B, Representative heat-evoked (40°C, horizontal filled bars) calcium influx responses in HEK 293 cells stably expressing TRPV4. Bath solution osmolarity is indicated. The 300 mOsm low-sodium (300/m) and 250 mOsm solutions contained equivalent NaCl concentrations and differed only by the presence or absence, respectively, of mannitol. In the bottom two traces the experiment was initiated in 300/m solution and was switched to 250 mOsm at the time indicated by the arrows. C, Summary of heat-evoked calcium responses at indicated osmolarities for cells stably transformed with control vector (P; open columns; n = 3–4) or TRPV4 (V4; filled columns;n = 5–9). Data represent the mean ± SEM of the indicated number of coverslips. Comparisons in A andC are with the appropriate 300 mOsm or 300/mcontrols. *p < 0.05; **p < 0.01; ***p < 0.001 (NS, not significant; unpaired t test).