Regulation of swimming by cell SIN1's firing frequency. A. Control. DP nerve stimulation elicits a swim episode 15 cycle in length. Timing of the DP nerve stimulation is represented by a bar.

During the next DP nerve induced swim episode, depolarization of cell SIN1 with a 1 sec current pulse rapidly hyperpolarizes cell 204 and terminates the swim episode. Note that depolarization of cell SIN1 causes a barrage of inhibitory postsynaptic potentials in cell 204.

When the preparation is not swimming, strong excitation of cell SIN1 elicits only a slight inhibitory response in cell 204. Cell SIN1 was depolarized by intracellular injection of current.