Figure 2. Inhibition of the directly elicited muscle twitch by tetrodotoxin in biopsy sections of human skeletal muscle. In the tetrodotoxin dose-response curve, each symbol represents one fiber bundle tested for one healthy (open symbols) or MH-susceptible (filled symbols) person. For each symbol, the percentage twitch height indicated in the figure is the value after subtraction of the twitch height at 400 nM tetrodotoxin (see Table 4). The curves are based on the values at 0–200 nM tetrodotoxin in Table 4without subtraction of the twitch height at 400 nM tetrodotoxin.