Potentiation by capsaicin of lidocaine's phasic impulse block in isolated rat sciatic nerve.
Compound action potentials (CAPs) of A- and C-fibres were recorded from isolated sciatic nerves of the rat to determine whether lidocaine-induced phasic impulse block was affected by low doses of capsaicin. Preceding impulse activity produced phasic reductions of the amplitudes of both A- (5.7 +/- 1.3%) and C-CAPs (20.7 +/- 7.0%) in drug-free solution. Capsaicin alone (50 microM) did not change the activity-induced reductions of the heights of both CAPs (A-CAP: 6.2 +/- 1.7%, C-CAP: 22.3 +/- 8.0%). Lidocaine (100 microM) caused differential phasic blocks between the A-CAP (20.1 +/- 3.7%; n = 7) and the C-CAP (33.8 +/- 4.9% n = 7). Lidocaine's phasic impulse block was potentiated after 30 min of subsequent capsaicin administration (A-CAP: 40.6 +/- 4.7%, n = 7; C-CAP: 48.8 +/- 5.5% n = 9). Capsaicin's phasic potentiating effects were reversed after 30 min of washing. These results suggest that capsaicin may be a useful agent for the reversible potentiation of phasic impulse blockade by lidocaine.
Shin
H C
HC
Department of Physiology, College of Medicine, Hallym University, Chunchon, Korea.
Park
H J
HJ
Raymond
S A
SA
D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D002211:Capsaicin / Q000494:pharmacology*; D004357:Drug Synergism; D066298:In Vitro Techniques; D008012:Lidocaine / Q000494:pharmacology*; D008297:Male; D009412:Nerve Fibers / Q000187:drug effects / Q000502:physiology; D009413:Nerve Fibers, Myelinated / Q000187:drug effects / Q000502:physiology; D051381:Rats; D012584:Sciatic Nerve / Q000187:drug effects* / Q000502:physiology
D008012:Lidocaine; D002211:Capsaicin