POTENTIATION BY CAPSAICIN OF LIDOCAINES TONIC IMPULSE BLOCK IN ISOLATED RAT SCIATIC-NERVE

Compound action potentials (CAPs) of A- and C-fibers were recorded fro m isolated sciatic nerves of the rat to determine whether tonic block of impulse conduction induced by lidocaine was affected by low doses o f capsaicin. Capsaicin alone (50 mu M) did not change the CAPs of eith er A- or C-fibers. Although the lower concentrations of capsaicin (5-3 0 mu M) caused no change of the tonic blocking action of lidocaine, 30 min of 50 mu M capsaicin administration did induce a significant pote ntiation of tonic block. Capsaicin's potentiating effects were partial ly reversed after 30 min of wash. These results suggest that capsaicin may be a useful agent for the potentiation of impulse blockade by lid ocaine.