The effects of curare in the cockroach. II. Blockage of nerve impulses by dTC.

Although for many years insects were believed to be insensitive to curare (Harlow, 1958; Hopf, 1952; Krupp, Lendle & Stapenhorst, 1952; Roeder, 1948, 1953; Roeder & Weiant, 1950; Usherwood, 1963), the recent report of Larsen, Miller & Yamamoto (1966) has demonstrated that insects are, indeed, sensitive to curare. Subsequent investigations (McCann, 1966; Flattum, Friedman & Larsen, 1967; Friedman, 1967) have been unable to elucidate the site or mechanism of insect curarization. However, studies of leg contraction in the cockroach (Friedman & Carlson, 1969) led us to the conclusion that curare most probably causes failure of contraction by preventing conduction of action potentials in motor nerve fibres. We furthermore proposed that blockage by curare of action potential conduction is the mechanism of insect curarization. This report supports our proposal by presenting electrophysiological evidence which indicates that curare (d-tubocurarine, dTC) blocks the conduction of action potentials in nerve fibres of the cockroach, Periplaneta americana.