Mammalian optic nerve fibers display two pharmacologically distinct potassium channels.
A suction electrode recording technique was used to study action potential characteristics of rat optic nerve fibers. Two pharmacologically distinct potassium channels are described. One is sensitive to 4-aminopyridine (4-AP) and the other to tetraethylammonium (TEA). 4-AP application leads to a substantial broadening of the optic nerve action potential, but TEA does not. 4-AP application also elicits a TEA-sensitive post-spike positivity, i.e. an intracellular hyperpolarization. From these results we suggest that the 4-AP-sensitive channel, not the TEA-sensitive channel, is primarily responsible for action potential repolarization of mammalian optic nerve fibers.
D015761:4-Aminopyridine; D000200:Action Potentials; D000631:Aminopyridines / Q000494:pharmacology; D000818:Animals; D001369:Axons / Q000502:physiology; D049832:Decapodiformes; D066298:In Vitro Techniques; D007473:Ion Channels / Q000502:physiology*; D007700:Kinetics; D009900:Optic Nerve / Q000502:physiology*; D011188:Potassium / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D019789:Tetraethylammonium; D013757:Tetraethylammonium Compounds / Q000494:pharmacology
D000631:Aminopyridines; D007473:Ion Channels; D013757:Tetraethylammonium Compounds; D019789:Tetraethylammonium; D015761:4-Aminopyridine; D011188:Potassium