Tricine selectively affects the activation gating of Ca_v2.3. (A) Representative current traces recorded in response to the I-V protocol (V_hold = −90 mV; depolarizing pulses from −30 to +10 mV) in HEPES (a) and Tricine solutions (b) containing 1 mM Ca²⁺ as a charge carrier. Highlighted current traces recorded in response to a −10-mV voltage step. (B) Peak current I-V relationships obtained in HEPES- or Tricine-based extracellular solutions. Data were fitted with GHK Eq. 1 (Table 1). (C) Voltage dependence of the effect of Tricine on Ca_v2.3. Ratio of peak current amplitudes (I_Tricine/I_HEPES) at each potential plotted as a function of potential. (D) Voltage dependence of activation of Ca_v2.3 measured in HEPES- and Tricine-based extracellular solutions. (E) Normalized and averaged Ca²⁺ currents ± SEM (shaded area) recorded in response to prolonged (3-s) depolarizing pulse to −10 mV in HEPES and Tricine solutions. Recordings were fitted with double-exponential function: I(t) = A_f exp(−t/τ_f) + A_s exp(−t/τ_s) + C. Corresponding values and statistics are in Table 1. (F) Steady-state inactivation curves, measured at +30 mV after 15-s-long conditioning prepulses.