General anesthetic block of a bifurcating axon

Axons with a low safety factor for conduction, namely the bifurcating motor neurons of the lobster deep extensor muscles, were tested for sensitivity to general anesthetic agents. Bath concentrations of 100-300 mM diethyl ether or 1.7-3.4 mM halothane were applied. The anesthetics blocked conduction of single action potentials in the branches before the main axon. Maximum following frequency of the branch point itself was reduced before the response to single stimuli was affected. Although the applied concentrations are slightly above those which correspond to general anesthesia, this large axon is relatively more sensitive than others of comparable diameter. These effects may have a role in the mechanism of general anesthesia, since even in the absence of frank conduction block, the pattern of impulse flow through the branch point may be significantly altered.