Acetylcholine and ciliary movement in the gill plates of Mytilus edulis

Acetylcholine has been known to act as a humoral transmitter of nerve impulses since 1921. As a result of work on the isolated auricles of the rabbit heart the hypothesis was put forward that acetylcholine has another function, namely, the control of rhythmic activity in various tissues for the performance of which it is produced locally. This hypothesis has been proved by work on ciliary movement in the gill plates of Mytilus edulis. Acetylcholine has been shown to be present in the gill plates by pharmacological assay and also by paper chromatography. A choline acetylase system has been shown to be present and also ‘true’ cholmesterase. The ciliary movement itself is modified by acetylcholine and also by eserine. Both these substances increase the movement in low concentration and depress it in high concentration. The ciliary movement is depressed by d-tubocurarine. These observations indicate that the nerve-free tissue of the gill plates can form acetylcholine, and that it is present there as a local hormone which controls the ciliary movement.