PIRTLE, T.J.; SATTERLIE, R.A.: Serotonergic Modulation of Ionic Currents Underlying Postinhibitory Rebound in Clione Swim Interneurons
Swimming in the pteropod mollusk, Clione limacina, is generated by two antagonistic groups of swim interneurons that reciprocally inhibit each other. One property of swim interneurons in each group that contributes to locomotor pattern generation is postinhibitory rebound (PIR). Serotonin has been shown to mediate changes in swim speed in reduced preparations of Clione by modulating the activity of swim interneurons in several ways. Serotonin causes baseline depolarization and spike narrowing, enhances PIR, and decreases the latency to peak PIR. Here we show results that suggest that the latency to peak PIR is mediated by an IA-like potassium current. Application of 5mM 4-aminopyridine (a blocker of IA) significantly decreased the mean latency to peak PIR by 56% (n=5, p<0.05). Additional data suggest that serotonin may modulate an Ih-like hyperpolarization activated inward current as observed from changes seen in the “sag potential” produced by hyperpolarization.
