[Effects of volatile anesthetics on conduction and maximum rate of rise of action potential upstroke in guinea-pig papillary muscles].

Using standard microelectrode techniques, effects of halothane, enflurane and isoflurane on the maximum rate of rise of action potential upstroke (Vmax) and conduction velocity of excitation were examined and compared with those of fast sodium channel blockers in isolated guinea-pig papillary muscles. Lidocaine and tetrodotoxin decreased the square of the conduction velocity in proportion to the decrease in Vmax. In contrast, halothane, enflurane and isoflurane only slightly affected Vmax, but decreased the conduction velocity in a concentration-dependent manner. These results suggest that these volatile anesthetics affect conduction velocity by a mechanism different from that of fast sodium channel blockers.