Effect of HYPO and the TRPV4 antagonist, HC-067047, on M-1 [Ca2+]i levels. A. [Ca2+]i response to HYPO (220 mOsm) in the presence and absence of HC-067047 (100 nM) and extracellular Ca2+ (0 Ca2+). In the absence of blocker (A), HYPO induces a biphasic time course with a peak increase in [Ca2+]i within 1–3 minutes followed by relaxation to pseudoplateau levels. Under 0 Ca2+ conditions, the increase in [Ca2+]i is markedly reduced except for a small transient increase in [Ca2+]i, indicative of Ca2+ release from internal stores. B. Effect of HYPO on peak [Ca2+]i levels (n=10). C. Summary effect of TRPV4 inhibition by HC-067047 and 0 Ca2+ on the peak change in [Ca2+]i given as a % of the control HYPO response. Data are presented for the HYPO response in control (HYPO, n = 5, 100% response), 1 nM (n = 4), 10 nM (n = 3), 100 nM (n = 3) HC-067047 and for 0 Ca2+ (n = 2). *P<0.05.