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Tension generation and increase in voltage-activated Na+ current by crotamine
A C Matavel1, D L Ferreira-Alves, P S Beirão
1Departamento de Bioquímica e Imunologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil.
European Journal of Pharmacology
|July 4, 1998
Summary
Crotamine, a South American rattlesnake toxin, significantly increases sodium (Na+) currents in frog muscle. This toxin affects the voltage dependence of channel inactivation, suggesting a novel mechanism of action.
Area of Science:
- Toxicology
- Neuroscience
- Biophysics
Background:
- Crotamine is a toxin found in South American rattlesnake venom.
- Sodium (Na+) currents are crucial for muscle and nerve function.
Purpose of the Study:
- To investigate the effects of crotamine on Na+ currents in frog skeletal muscle.
- To elucidate the mechanism by which crotamine modulates Na+ channel activity.
Main Methods:
- Loose patch clamp technique was employed to measure macroscopic Na+ currents.
- Experiments were conducted on isolated frog skeletal muscle fibers.
Main Results:
- Crotamine (50 microM) increased peak Na+ current by 50% (P < 0.05).
- A +8 mV shift in the voltage dependence of Na+ current inactivation was observed.
- Other Na+ current parameters, including activation and reversal potential, remained unaffected.
Conclusions:
- Crotamine enhances Na+ currents by altering channel inactivation.
- The toxin may inhibit the direct closed-to-inactivated state transition of Na+ channels.
- This action forces channels through open states, increasing current flow.