Application of quinidine on rat sciatic nerve decreases the amplitude and increases the latency of evoked responses

Purpose: Multi-modality electrophysiological techniques were performed to assess the effects of quinidine on peripheral nerve conduction.

Methods: Twenty-seven rats were treated with 1, 3, and 5 μmol quinidine in 0.1 ml 5 % glucose. The mixed-nerve somato-sensory evoked potential (M-SSEP), dermatomal-SSEP (D-SSEP), and compound muscle action potentials (CMAP) were evoked and recorded. After positioning Gelfoam strips saturated with quinidine and 5 % glucose around the left and right sciatic nerves, potentials were measured at baseline, immediately after treatment, every 15 min for the 1st hour, and every 30 min for the next 3 h. After 2 weeks, the walking behaviors and potentials were again analyzed and myelinated fibers in the sciatic nerve were counted.

Results: Quinidine applied directly to sciatic nerves reduced the amplitude and prolonged the latency in SSEPs and CMAP, compared to baseline and the contralateral right limbs (controls). This persisted for at least 4 h. After 2 weeks, electrophysiological tests and walking behavior showed no significant difference between the controls and experimental limbs. There was also no difference in the number of myelinated fibers in the sciatic nerves.

Conclusions: Quinidine decreases amplitude and prolongs latency in the sciatic nerve in a dose-related manner without local neural toxicity.