Repetitive depolarization induces calcium and PKA-dependent sensitization of calcium currents in small diameter rat DRG neurons. (A) Normalized I-V curves, V0.5_act, and representative traces for calcium currents (ICa) before and 60 s after applying a train of 10 1-s-long depolarizations to 0 mV. (B) Normalized I-V curves, V0.5_act, and representative traces for barium currents (IBa) before and 60 s after applying a train of 10 1-s-long depolarizations to 0 mV. (C) Normalized I-V curves, V0.5_act, and representative traces for calcium currents (ICa) before and 60 s after applying a train of 10 1-s-long depolarizations to 0 mV. DRG neurons were preincubated with H89 (25 µM, 1 h). Numbers of analyzed neurons are given in parentheses. Data represent means ± SEM of at least three animals. Currents underlying the I-V curves were elicited from −40 to +50 mV in 10-mV increments with 5 mM Ca²⁺ or Ba²⁺ as charge carrier. The holding potential was −90 mV. Paired t test; *, P < 0.05.