Fig. 1.

4-AP differentially potentiates L-type and N-type, but not P/Q-type, currents. (A) Original current traces show the concentration-dependent effects of 4-AP on L-type (Cav1.2), P/Q -type (Cav2.1), and N-type (Cav2.2) currents in HEK293 cells cotransfected with α₂δ1 and Cavβ3. Ba²⁺ currents (I_Ba) were elicited by a test pulse from a holding potential of –90 mV to 0 mV for 200 milliseconds. (B) Concentration-response relationships of 4-AP on L-type, P/Q-type, and N-type currents reconstituted with α₂δ1 and Cavβ3 in HEK293 cells. Note that only the L-type Ca²⁺ channel was potentiated by 4-AP at concentrations <1 mM. *P < 0.05, **P < 0.01 compared with respective baseline controls before 4-AP application (repeated measures analysis of variance followed by Dunnett’s post hoc test).