Related Experiment Videos
C fiber generates a slow Na+ spike in the frog sciatic nerve
J Kobayashi1, M Ohta, Y Terada
1Department of Prosthetic Dentistry I, Faculty of Dentistry, Kyushu University, Fukuoka, Japan.
Neuroscience Letters
|November 12, 1993
Summary
This study reveals bullfrog C-fibers use a unique, tetrodotoxin-resistant sodium channel for action potentials, unlike faster A-fibers. This finding advances understanding of nerve impulse generation in different fiber types.
Area of Science:
- Neuroscience
- Physiology
- Electrophysiology
Background:
- Nerve fibers (A and C) transmit signals differently.
- Understanding ion channel mechanisms is crucial for nerve function.
Purpose of the Study:
- To investigate the properties of A and C fibers in bullfrog sciatic nerves.
- To identify the ion channels responsible for action potential generation in these fibers.
Main Methods:
- Agents were applied via perfusing solutions between electrodes.
- Compound action potentials (CAPs) were recorded.
- Sensitivity to tetrodotoxin (TTX) and Na(+)-free solutions was tested.
- Effects of Ca2+ channel blockers were assessed.
Main Results:
- A beta and A delta fiber CAPs were sensitive to TTX and abolished in Na(+)-free solution.
- C fiber CAPs were TTX-insensitive but disappeared in Na(+)-free solution.
- C fiber CAPs were unaffected by Ca2+ channel blockers.
- C fiber chronaxy (2 ms) and conduction velocity (0.70 m/s) suggest a large time constant (2.88 ms).
Conclusions:
- Bullfrog C-fibers likely utilize a slow, TTX-resistant sodium channel for action potentials.
- This contrasts with the TTX-sensitive channels in A-fibers.
- The findings provide insights into the diversity of ion channel function in neuronal signaling.