Effects of chlorpromazine on spiral cord reflex mechanisms,

Abstract

The effects of chlorpromazine (CPZ) on the patellar reflex and segmentally evoked spinal cord potentials were determined in the high spinal and hemisectioned spinal cat preparations. CPZ in doses of 1-32 mg/kg given intravenously (as an accumulative dose) produced no statistically significant alteration of the patellar reflex and segmentally evoked monosynaptic potentials. The segmentally evoked polysynaptic potential was significantly depressed (1-32 mg/kg). CPZ was shown to cause a significant depression of facilitation and inhibition of the patellar reflex produced by electrical stimulation of the lateral and ventral funiculi of cervical cord segments 1 and 2. Facilitation of the patellar reflex produced by contralateral stimulation of the sciatic nerve was resistant to doses of CPZ but was significantly depressed by 4 mg/kg. Patellar reflex inhibition produced by ipsilateral sciatic nerve stimulation was never observed to be depressed by doses used in this study. The patellar reflex recorded ipsilateral to a high cervical (C1) and mid-thoracic (T6) hemisection of the spinal cord was resistant to doses of CPZ (1-8 mg/kg) while the contralateral patellar reflex was depressed. The mean arterial blood pressure was significantly elevated by doses of CPZ (4-32 mg/kg). The evidence presented indicates the internuncial neuron of the spinal cord as a probable site of chlorpromazine action. Possible mechanisms of blood pressure elevation are discussed.