Figure 4

Activation (left panels) and inactivation I-V curves (right panels of each pair) (mean of I₁ or I₂ ± standard error of mean (SEM) against each V₁ excursion) in response to caffeine challenge at a concentration of 0.5 mM in the absence (A) or the presence (B) of 10 μM dantrolene. Experiments first obtained families of I_Na records before addition of caffeine in (A(i)), (B(i)). Families of I_Na records then obtained in intervals (ii) 1–10 minutes, (iii) 11–25 minutes (iv) 26–40 minutes and (v) 41–55 min intervals after adding 0.5 mM caffeine.