ASSESSING LOCAL-ANESTHETIC EFFECT USING THE MOUSE TAIL-FLICK TEST

We used the tail flick test to quantify duration of local anesthetic-i nduced conduction block in the mouse. Using a baseline tail flick late ncy (TFL) between 1.0 and 2.5 sec, sensory block was considered presen t if TFL was greater-than-or-equal-to 4 sec. Two 20-muL local anesthet ic injections were made on opposite sides of the tail base. TFL was te sted every 10 min, and local block duration was interpreted as the tim e to return of TFL to < 4 sec. We tested three different concentration s of procaine (1%, 2%, and 4%), tetracaine (0.125%, 0.5%, and 1%), and lidocaine (0.5%, 1%, and 2%) with and without epinephrine. The testin g method could discriminate between the duration of the various local anesthetic concentrations used. For the 1% concentrations, the duratio n of sensory block was 2 +/- 4 min (S.D.) for procaine, 2- +/- 10 min for lidocaine, 40 +/- 10 min for tetracaine, and 66 +/- 15 min for lid ocaine with epinephrine. We found this to be a simple and reliable mea ns of assessing local anesthetic conduction block in the mouse.