Figure 8. Trpv1−/− modifies RGC physiology with elevated IOP. A, IOP in C57 and Trpv1−/− mouse eyes used for RGC physiology remained elevated for ∼4 weeks (25–28 d) after microbead injection compared with saline injection (*p < 0.001, two-sided t test for each cohort). IOP (mean ± SEM) was similar in C57 and Trpv1−/− mice for both saline-injected (14.63 ± 0.78 vs 14.73 ± 0.79 mmHg, respectively; p = 0.523) and microbead-injected (19.47 ± 0.97 vs 19.77 ± 0.94 mmHg; p = 0.559) eyes (two-sided t test for each). B, A C57 RGC filled with 1% Lucifer yellow during whole-cell patch-clamp recording after IOP elevation shows ramified dendrites and axon (arrow). Scale bar, 50 μm. C, Microbead-induced IOP elevation increases spontaneous firing of action potentials under current-clamp in C57 but not Trpv1−/− RGCs. D, Spontaneous firing rate (mean ± SEM) increased significantly for RGCs in C57 microbead-injected retinas (12.43 ± 1.88 Hz, n = 27) compared with saline-injected retinas (5.65 ± 1.20 Hz, n = 14; *p = 0.025, two-sided t test). RGCs in Trpv1−/− microbead-injected retinas demonstrated significantly less spontaneous activity compared with their C57 counterparts (4.44 ± 0.77 Hz, n = 14; †p = 0.006, two-sided t test), but were similar to their own saline-injected RGCs (n = 20; p = 0.33, two-sided t test). E, Traces show RGC action potentials induced by 25 or 50 pA depolarizing current steps for cells with low spontaneous rates (<0.5 Hz); RGCs in Trpv1−/− retinas typically required more depolarization to reach a threshold rate of firing >3 Hz. F, Depolarizing current (mean ± SEM) required to induce action potentials in RGCs with low spontaneous rates (< 0.5 Hz) was greater in Trpv1−/− microbead-injected retinas (62.50 ± 9.32 pA, n = 13) compared with Trpv1−/− saline-injected retinas (34.62 ± 6.03 pA, n = 10; *p = 0.004, two-sided t test) and compared with C57 microbead-injected retinas (42.50 ± 7.72 pA, n = 20; †p = 0.011, two-sided t test). The threshold current was the same for C57 microbead- and saline-injected retinas (41.30 ± 8.11 pA, n = 23) vs Trpv1−/− saline-injected retinas (p = 0.86, one-way ANOVA on ranks).