Fig. 8. A, Comparison of the HVA calcium current amplitude (current–voltage relationship curves) between rhythmic (R, filled circles; n = 10) and nonrhythmic (nR, open circles; n= 21) VRG neurons. B, Two examples for a qualitative characterization of different subtypes of the HVA calcium current in VRG neurons (left figure, rhythmic;right figure, nonrhythmic). Current amplitude (for detailed protocol description, see Results) is plotted against time. Specific calcium channel blockers ω-conotoxin MVIIA (to block N-type calcium channels), ω-conotoxin MVIIC (to block Q-type calcium channels), ω-agatoxin IVA (to block P-type calcium channels), and nifedipine (to block L-type calcium channels) have been applied as indicated by the dotted lines. MVIIA, ω-Conotoxin MVIIA; MVIIC, ω-conotoxin MVIIC;AgaIVA, ω-agatoxin IVA; Nif, nifedipine; CdCl, cadmium chloride.