Effects of chlorpromazine on spinal cord reflex mechanisms.

-The effects of chlorpromazine (CPZ) on the patellar reflex and segmentally evoked spinal cord potentials were determined in the high spinal and hemiscctioned 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 polysynapti¢ potential was significantly depressed (1-32 ms/ks). 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 rag/ks. Patellar reflex inhibition produced by ipsflateral sciatic nerve stimulation was never observed to be depressed by doses used in this study. The patellar reflex recorded ipsilateral to a high cervical (CI) and mid-thoracic (T6) hemiscction 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 rag/ks). The evidence presented indicates the internuncial neuron of the spinal cord as a probable site of chlorpromazine action. Possible meehanisms of blood pressure elevation are discussed.