The effect of new local anaesthetics on tracheal and anococcygeal smooth muscle.

The effects of pentacaine and heptacaine were compared with that of procaine on the isolated tracheal smooth muscle of guinea-pigs and anococcygeal muscle of rats. Pentacaine increased the initial tone of the tracheal smooth muscle. In higher concentration however pentacaine and heptacaine induced smooth muscle relaxation. Pentacaine diminished the action of histamine on the tracheal smooth muscle and both pentacaine and heptacaine depressed the effects of noradrenaline and acetylcholine on anococcygeal muscle.