Fig. 3.
Ca2+ dependence of isoflurane-activated type 3 inositol trisphosphate receptor (InsP3R-3) channel. (A) Typical single-channel current traces of InsP3R channels activated by 400 μM isoflurane in free Ca2+ concentration ([Ca2+]i) of 900 nM. Currents shown were recorded at room temperature with applied potential (Vapp) = −40 mV, and arrow indicates the closed channel current level. (B) [Ca2+]i dependence of InsP3R-3 channel open probability (Po) in 400 μM isoflurane. Error bars indicate SEM, and number of experiments analyzed is tabulated. Note the logarithmic channel Po axis. Low channel Po (<0.01, marked with §) were observed in all [Ca2+]i examined other than 2 μM. There is no statistically significant difference among these low channels Po (P > 0.05, ANOVA test). These channel Po were so low that the number of active channel(s) (N) in the membrane patch cannot be accurately determined. Thus, the data plotted are effectively the NPo value, which may be an overestimate of the actual Po value.