Sensitivity of sensory axons to lidocaine nerve block in rats.
The aim of the present study was to test the sensitivity of different classes of sensory axons to lidocaine 2 and 4% nerve block. The basic approach was to examine changes in compound action potential (CAP) of A and C axons of the rat sural nerve induced by 2 or 4% lidocaine nerve block in vitro. CAP in control sural nerves (n = 6 for each experimental group) before nerve block was induced, consisted of the early component (A axons: 0.3 +/- 0.02 ms) and the late component (C axons: 12.2 +/- 1.14 ms) with peak voltage amplitudes 4.4 +/- 1.4 mV and 0.04 +/- 0.02 mV, respectively. Lidocaine 2% nerve block completely abolished the amplitude of CAP of C axons and depressed the amplitude of CAP of A axons to about 20 % of control level. Doubled concentration of lidocaine significantly decreased time taken to develop maximal depression of CAP and significantly increased excitation threshold of sensory A axons, but not of sensory C axons. However, 4% lidocaine did not affect the maximal depression of CAP of sensory A axons. These results support the view, that C axons are more sensitive to lidocaine nerve block than A axons. In addition, our results suggest a population of sensory A axons which is non-sensitive to 2% and 4% lidocaine.
Potocnik
I
I
Center of Dental Diseases, Dental Department, University Medical Center, Ljubljana, Slovenia.
Tomsic
M
M
Bajrović
F
F
D000200:Action Potentials / Q000187:drug effects; D000779:Anesthetics, Local / Q000494:pharmacology*; D000818:Animals; D001369:Axons / Q000187:drug effects* / Q000502:physiology; D004305:Dose-Response Relationship, Drug; D005260:Female; D008012:Lidocaine / Q000494:pharmacology*; D009407:Nerve Block; D009475:Neurons, Afferent / Q000187:drug effects* / Q000648:ultrastructure; D051381:Rats; D017208:Rats, Wistar; D013497:Sural Nerve / Q000166:cytology / Q000187:drug effects
D000779:Anesthetics, Local; D008012:Lidocaine