Effects of the Calcium Channel Blocker Verapamil on Spinal Reflexes

Abstract

Effects of calcium channel blocker verapamil on spinal reflexes were studied. Verapamil 5, 50, ?M locally. 10, 20 mg/kg was administrated intraperitoneally and 10, 50, 100 ?M locally. Experiments on adult spinal cats (n=10) were conducted. Animals weighing 1.5-3 kg were anesthetized with ketamine (45 mg/kg intramuscular) and artifically ventilated. Animals were spinalized at C1 level and a laminectomy was performed in the lumbosacral region. The ventral and dorsal roots of segment L5 were isolated. A polyethylene cannule was introduced into the carotid artery to monitor blood pressure, which was kept above 100 mmHg. The dorsal root of segment L5 placed on a silver-silver chloride wire electrode for electrical stimulation. The reflex potentials were recorded from the ipsilateral L5 ventral root, mounted on a silver-silver chloride wire electrode. Both systemic and local application of verapamil inhibited reflexes (p<0.05). The latency of reflexes was considerably increased as a results of systemic 20 mg doses (p<0.05). These results show the possible presence of voltage-dependent calcium channels in the spinal cord and these channels may play an important role to regulate reflex responds.