SEROTONIN AND ADENOSINE TRIPHOSPHATE: SYNERGISTIC EFFECT ON THE BEAT FREQUENCY OF CILIA OF MUSSEL GILLS.

For each tenfold increase in the concentration of serotonin in the range 10(-7) to 10(-4)M, the beat frequency of the lateral cilia of the gills of the freshwater mussel Elliptio complanatus increases by approximately two beats per second over the mean frequency of 14.5 beats per second for control gills perfused with 0.04M potassium chloride. The addition of 10(-6) to 10(-3)M concentrations of adenosine triphosphate has no detectable effect on the beat frequency. The addition of both serotonin and 10(-4)M adenosine triphosphate increases the frequency by two beats per second more than does the addition of serotonin alone.