Tetrodotoxin-resistant Na+ spikes of C fibers have at least two subtypes in the isolated bullfrog sciatic nerve.
The C fiber compound action potentials (C-CAPs) were studied for their properties with the vaseline gap method from the isolated bullfrog sciatic nerve. Two components (the fast and the slow C-CAPs) were found to be Na+ dependent and tetrodotoxin-resistant. The conduction velocities of the fast and the slow C-CAPs were 0.61 +/- 0.06 m/s (n = 13) and 0.42 +/- 0.05 m/s (n = 8), respectively; their time constants were 11.4 +/- 1.7 m/s and 16.3 +/- 1/7 ms, respectively, with both parameters being significantly different at P < 0.01. The slow C-CAP had about 1.3 times higher threshold than that of the fast C-CAP, with a significant difference (P < 0.01). They showed differential sensitivity to lidocaine and Cd2+. Capsaicin reduced the amplitudes of both fast and slow C-CAPs, but not abolished. These findings indicate that C fibers have at least two subtypes with different properties.
Kobayashi
J
J
Department of Prosthetic Dentistry I, Faculty of Dentistry, Kyushu University, Fukuoka, Japan.
Ohta
M
M
Terada
Y
Y
D000200:Action Potentials / Q000187:drug effects / Q000502:physiology; D000779:Anesthetics, Local / Q000494:pharmacology; D000818:Animals; D002104:Cadmium / Q000494:pharmacology; D002211:Capsaicin / Q000494:pharmacology; D004558:Electric Stimulation; D004594:Electrophysiology; D008012:Lidocaine / Q000494:pharmacology; D009412:Nerve Fibers / Q000187:drug effects / Q000502:physiology*; D011892:Rana catesbeiana; D012584:Sciatic Nerve / Q000166:cytology* / Q000502:physiology; D012964:Sodium / Q000502:physiology*; D013779:Tetrodotoxin / Q000494:pharmacology*
D000779:Anesthetics, Local; D002104:Cadmium; D013779:Tetrodotoxin; D008012:Lidocaine; D012964:Sodium; D002211:Capsaicin