A model for the fast 4-aminopyridine effects on amphibian myelinated nerve fibres. A study based on voltage-clamp experiments.
The effect of 4-aminopyridine (4-AP) on the potassium currents in the node of Ranvier in myelinated nerve fibres was investigated with the voltage-clamp technique. The potential and time dependence of the currents in solutions with a high potassium concentration (114.5 mM) were studied. The block of the tail current was found to be less than that of the corresponding current during a potential step. Also, the time-course of the tail current was modified. In order to explain these findings, kinetic models of the 4-AP action were constructed and analysed numerically. A simple four-state model, in which 4-AP interacts only with open channels and where the binding is diphasically potential dependent, was found to account for the effects.
Arhem
P
P
Nobel Institute for Neurophysiology, Karolinska Institute, Stockholm, Sweden.
Johansson
S
S
D015761:4-Aminopyridine / Q000494:pharmacology*; D000818:Animals; D007700:Kinetics; D008959:Models, Neurological; D009413:Nerve Fibers, Myelinated / Q000187:drug effects*; D015221:Potassium Channels / Q000187:drug effects; D011901:Ranvier's Nodes / Q000187:drug effects; D014982:Xenopus laevis
D015221:Potassium Channels; D015761:4-Aminopyridine