Fig. 8.
Acceleration of the heartbeat rhythm by FMRFamide.A, The period of the activity rhythm in oscillator heart interneurons (HN) is reduced from 7.5–8.5 sec to ∼6 sec by bath application of 5 × 10−8m FMRFamide. B, The effect of FMRFamide is mimicked in the model heart interneurons by introducing IKF and shifting the steady-state inactivation curve of IK1 by −10 mV (i.e., to the left). Simon et al. (1992) demonstrated that FMRFamide produced such a negative shift in steady-state inactivation of IK1. HN cells are indexed by ganglion number and body side.