4-aminopyridine activates a cholinergic chloride conductance in isolated Helix neurons.
Isolated Helix neurons were internally perfused under voltage-clamp, with drugs applied by the 'concentration clamp' which allowed an extremely rapid switching of the external solution. 4-Aminopyridine (4-AP) at more than 3 X 10(-4) M induced a chloride current (ICl) which could be blocked by D-tubocurarine. Acetylcholine (ACh) also induced ICl which was similarly blocked. Simultaneous application of 4-AP and ACh resulted in potentiation of ICl over the sum of respective currents. When preceded by either one, the other ICl was reduced in size, showing cross-desensitization. These data indicate that 4-AP activates ICl by binding to the cholinergic receptors, and reduces ACh-induced ICl by desensitizing a common receptor-channel complex.
D015761:4-Aminopyridine; D000109:Acetylcholine / Q000008:administration & dosage; D000631:Aminopyridines / Q000008:administration & dosage / Q000494:pharmacology*; D000818:Animals; D002712:Chlorides / Q000378:metabolism*; D004347:Drug Interactions; D005724:Ganglia / Q000187:drug effects*; D006372:Helix, Snails; D066298:In Vitro Techniques; D007473:Ion Channels / Q000187:drug effects*; D011950:Receptors, Cholinergic / Q000187:drug effects*; D012908:Snails
D000631:Aminopyridines; D002712:Chlorides; D007473:Ion Channels; D011950:Receptors, Cholinergic; D015761:4-Aminopyridine; D000109:Acetylcholine