Effects of 4-aminopyridine on the action potential and the after-hyperpolarization of cat spinal motoneurons.
In cats under pentobarbital anaesthesia, intramotoneuronal administrations of 4-aminopyridine significantly prolong the falling phase of the antidromic action potential but have much less effect on the orthodromic action potential. 4-aminopyridine probably blocks the fast K channels involved in the repolarization of the membrane and indirectly activates ionic channels through enhancement of synaptic transmission, also suggested by the potentiation of excitatory postsynaptic potentials. In many cells, 4-aminopyridine depresses the amplitude and prolongs the time course of the after-hyperpolarization; therefore 4-aminopyridine may also partly block Ca2+-activated K+ channels.
D015761:4-Aminopyridine; D000200:Action Potentials / Q000187:drug effects; D000631:Aminopyridines / Q000494:pharmacology*; D000818:Animals; D002118:Calcium / Q000502:physiology; D002415:Cats; D007473:Ion Channels / Q000187:drug effects*; D008564:Membrane Potentials; D009046:Motor Neurons / Q000187:drug effects*; D011188:Potassium / Q000494:pharmacology; D013116:Spinal Cord
D000631:Aminopyridines; D007473:Ion Channels; D015761:4-Aminopyridine; D011188:Potassium; D002118:Calcium