Evaluation of the antinociceptive effects of lidocaine and bupivacaine on the tail nerves of healthy rats

This study was designed to develop a simple and effective model of tail nerve block without general anaesthesia and surgical incision, to assist in exploring and studying new local anaesthetics. Tail nerves of adult, male Sprague-Dawley rats were blocked by injecting 1% lidocaine and 0.5% bupivacaine, respectively. To evaluate the tail nerve block model, the effects of tail nerve blocks induced by two classical local anaesthetics were assessed and compared by recording disappearance and recovery time of thermal and mechanical nociception. The results showed that thermal and mechanical nociception of the tail disappeared after application of local anaesthetics but were unchanged by normal saline. No abnormal results were found in both the 3-day observation period and the pathological study, and pain thresholds of all rats recovered fully. We have thus developed an easily operated, reliable and reversible model of tail nerve block for conscious rats that can be used to evaluate efficacy, safety and pharmacokinetics of new local anaesthetics and additives.