Tricine substitution for HEPES produces no effect on activation gating of Ca_v2.2 and Ca_v3.2 cannels. (A and D) Representative Ca_v2.2 (A) and Ca_v3.2 (B) currents recorded at +5 and −30 mV, respectively, in HEPES and Tricine solutions. (B and E) Normalized ratios of peak current amplitudes for Ca_v2.2 (B; n = 6) and Ca_v3.2 (E; n = 9) channels. (C and F) Normalized and averaged I-V relationships measured in HEPES and Tricine solutions for Ca_v2.2 (C; n = 6) and Ca_v3.2 (B) channels. Data acquired from each cell were fitted with GHK Eq. 1 (Ca_v2.2: HEPES V_1/2 = −1.8 ± 1.0 and k = 4.5 ± 0.2 mV; Tricine V_1/2 = −3.8 ± 0.9 and k = 4.6 ± 0.2 mV; n = 6; and Ca_v3.2: HEPES V_1/2 = −47.4 ± 1.7 and k = 6.1 ± 0.2 mV; Tricine V_1/2 = −48.7 ± 1.2 and k = 6.0 ± 0.3 mV; n = 4).