Neural Control of Heart Beat in the Pteropod Mollusc Cuone Limacina: Coordination of Circulatory and Locomotor Systems

1. In the intact pteropod mollusc Clione limacina a correlation between heart beat and locomotor activity has been found. In freely swimming Clione, pauses in locomotor activity arose spontaneously with intervals of a few minutes. During these pauses, the heart stopped beating. A link between the heart and locomotor activity was also observed during defensive reactions: mechanical stimulation of the head resulted in the termination of both locomotion and heart beating, while stimulation of the tail accelerated both the locomotor and the heart rhythms. After transection of the medial abdominal nerve supplying the heart, the link between heart rate and locomotor activity disappeared. The heart rhythm accelerated during hunting behaviour of Clione. 2. Four efferent neurones controlling heart beat were found: one heart excitor (HE) in the left pedal ganglion, and three heart inhibitors (HI) in the left abdominal ganglion. The HE exerted an inhibitory action upon the His. 3. Spontaneous or reflex activation of the locomotor generator was accompanied by excitation of the HE and by inhibition of the His, while spontaneous or reflex inhibition of the locomotor generator was accompanied by inhibition of the HE and by excitation of the His. These effects were due, at least partly, to the direct action of the neurones of the locomotor generator upon the HE and His.