We have investigated the effects of verapamil, which blocks L-type calcium channels on spinal monosynaptic reflexes in spinalized cats. Adult cats (n=10) weighing 1.5-3 kg were anaesthetized with ketamine (50 mg/kg, IM) and the ventral and dorsal roots of segment L5-S2 were isolated after laminectomy. The lateral and medial gastrocnemius nerves were placed on an Ag-AgCl wire electrode for stimulation through an isolation unit. The reflex potentials were recorded from the ipsilateral L7 ventral root. The intraperitoneal administration of verapamil significantly decreased the amplitude of the reflex response (P<0.05). Our results suggest that L-type calcium channels in the spinal cord may play an important role in regulating the reflex response.