|Tetrodotoxin affects sodium gating current in squid giant axon|
Ichikawa, M.; Matsumoto, G. (1995). Tetrodotoxin affects sodium gating current in squid giant axon, in: Abbott, N.J. et al. (Ed.) Cephalopod neurobiology: neuroscience studies in squid, octopus and cuttlefish. pp. 119-129
In: Abbott, N.J.; Williamson, R.; Maddock, L. (Ed.) (1995). Cephalopod neurobiology: neuroscience studies in squid, octopus and cuttlefish. Oxford University Press: London. ISBN 0-19-854790-0. 542 pp., more
|Authors|| || Top |
- Ichikawa, M.
- Matsumoto, G.
Tetrodotoxin (TTX) , a cationic toxin which specifically blocks the sodium current, has long been believed to plug the ion-selective filter without any significant effect on the gate current. The guanidinium group of TTX is thought to bind to the charge of the filter in particular. In the present paper we provide experimental evidence that, instead, TTX binds to the gating site of the sodium channel in the squid giant axon to inhibit the transition primarily between the final closed state and the open state. This has been concluded as a result of the following experimental findings: (1) The gating current contains a TTX-sensitive component, a part of the gating current which can be specifically blocked by TTX in a concentration-dependent manner. (2) The variation with time of the running integral of the TTX-sensitive component is consistent with that of the rising phase of the sodium current. (3) The TTX-sensitive gating component is greatly affected by the presence and absence of sodium inactivation.