title: Effect of 4-aminopyridine on transmitter release in synaptosomes.
abstract: The effect of 4-aminopyridine (4-AP) on the release of labeled transmitters in mouse brain synaptosomes was studied in a superfusion system. 4-AP at microM concentrations notably stimulated the spontaneous release of labeled GABA and glutamate, and of acetylcholine (ACh) derived from tritiated choline. No effects on the release of labeled alpha-aminoisobutyric acid were observed. The stimulation of GABA and ACh release was dependent on the presence of Ca2+ in the superfusion media, whereas the effect on glutamate release was more variable and no clear Ca2+-dependence was observed. In contrast to these results, 4-AP did not have any effect on the release of the above transmitters stimulated by K+-depolarization in the presence of Ca2+. These results are discussed in terms of the possible participation of Ca2+ in the action of 4-AP on spontaneous transmitter release in isolated nerve endings.
mesh_terms: D015761:4-Aminopyridine; D000109:Acetylcholine / Q000378:metabolism; D000631:Aminopyridines / Q000494:pharmacology*; D000818:Animals; D001921:Brain / Q000187:drug effects*; D002118:Calcium / Q000494:pharmacology; D046508:Culture Techniques; D051379:Mice; D018377:Neurotransmitter Agents / Q000378:metabolism*; D011188:Potassium / Q000494:pharmacology; D013268:Stimulation, Chemical; D009435:Synaptic Transmission / Q000187:drug effects; D013574:Synaptosomes / Q000187:drug effects*; D005680:gamma-Aminobutyric Acid / Q000378:metabolism
chemical_list: D000631:Aminopyridines; D018377:Neurotransmitter Agents; D005680:gamma-Aminobutyric Acid; D015761:4-Aminopyridine; D000109:Acetylcholine; D011188:Potassium; D002118:Calcium