Zolmitriptan inhibits polysynaptic EPSPs in motoneurons of chronic spinal rats. A: PIC-mediated plateau potential and sustained firing (LLR) evoked by dorsal root stimulation (0.1-ms pulse, 3×T) in a motoneuron at rest (top trace; −72 mV, without injected current; spikes clipped). With a hyperpolarizing bias current to prevent PIC activation, the same stimulation only evoked a polysynaptic EPSP, with short- and long-duration components indicated (bottom trace; motoneuron at −80 mV). B: in the same motoneuron, zolmitriptan (1 μM) eliminated the plateau and LLR evoked by dorsal root stimulation (top trace) and inhibited the short and long EPSPs (hyperpolarized, bottom trace).