OBJECTIVE

To estimate local anesthetic effect of ethercaine on tail response in mice under laser exposure (tail-flick) and evoked M-response of the biceps femoris muscle following sciatic nerve stimulation.

MATERIAL AND METHODS

The study was performed under acute experimental conditions on 18 F1 BxD mice weighing 26-32 g and 24 male Wistar rats weighing 190—260 g. We used 1% ethercaine solution based on 4% micellar aqueous solution of Kolliphor ELP. A 4% aqueous solution of Kolliphor ELP was used as a negative control, and a 2% lidocaine solution — as a comparison drug. The drugs were injected symmetrically (0.03 ml) on both sides at the root of the tail. The tail-flick test was performed every 5 minutes starting from the 5^th minute after administration for 60 minutes. Sciatic nerve stimulation was carried out using rectangular electrical pulses with a duration of 0.1 ms (Nihon Kohden stimulator). We recorded electrical signals from the muscle using bimodal amplifier (Biola) and digitized these signals using 10-channel converter PPSh-10 (Biola).

RESULTS

Injections of 2% lidocaine solution and 1% ethercaine solution in 4% Kolliphor ELP led to comparable local anesthetic effect in proximal tail for 15—25 minutes. Local anesthetic effect in distal root was observed only for 2% lidocaine. Application of 1% ethercaine solution in 4% Kolliphor ELP led to higher threshold current strength and lower M-response amplitude. However, this effect was much weaker compared to lidocaine.

CONCLUSION

A 1% ethercaine solution in 4% Kolliphor ELP showed local anesthetic effect on the tail-flick infiltration anesthesia model. This effect is comparable to the effect of lidocaine. However, ethercaine demonstrates significantly less activity in conduction anesthesia model on sciatic nerve and no activity in tail-flick conduction anesthesia model. These results allow us to evaluate applicability of ethercaine in various types of anesthesia.