Figure 2

Involvement of TRPV4 receptor in hypotonicity-induced increase of TTX-S current. A. The plot shows the increase of TTX-S current by TRPV4 receptor agonist 4α-PDD at concentrations of 0.03-30 μM. The dose-response curve fits to Hill equation with EC₅₀ being 1.07 μM and n being 1.08. B. The increase of TTX-S current by hypotonicity was markedly attenuated by TRPV4 receptor antagonists RR and GdCl₃. Additionally, 4α-PDD-induced response was also significantly blocked by RR and GdCl₃. In the presence of RR or GdCl₃, the increase of TTX-S current by 4α-PDD (1 μM) was attenuated from 39.93 ± 6.04% to 7.36 ± 0.91% (unpaired t-test, P < 0.01) and to 6.11 ± 2.57% (unpaired t-test, P < 0.01), respectively. C. I-V curve shows the voltage-current relationship of TTX-S current before and during 4α-PDD (1 μM) treatment. D. In the presence of 4α-PDD (1 μM), G-V curve shifted to the hyperpolarizing direction, with V₀.₅ being -35.33 ± 1.32 mV and -43.67 ± 3.72 mV (n = 8, paired t-test, P < 0.05), k being 3.31 ± 0.98 and 3.11 ± 0.68 (n = 8, paired t-test, P > 0.05) before and during 4α-PDD treatment, respectively. E. There was no significant difference in inactivation-voltage curve before and during 4α-PDD treatment. V₀.₅ were -71.19 ± 4.15 mV and -72.72 ± 3.94 mV (n = 9, paired t-test, P > 0.05), k were -10.01 ± 1.05 and -10.94 ± 1.41 (n = 9, paired t-test, P > 0.05) for control and 4α-PDD group, respectively.