title: 4-Aminopyridine-induced ultrastructural alterations of pinched-off nerve terminals from rat cerebral cortex.
abstract: Pinched-off nerve terminals (synaptosomes) from rat cerebral cortex were depolarized with 60 mM KCl and treated with 20 mM 4-aminopyridine in order to evaluate ultrastructural alterations. The empty presynaptic terminals were counted and their number was given as a percentage of the normal terminals. The proportion of empty terminals increased from 10.47 +/- 1.56% to 32.45 +/- 1.88% (P less than 0.001) following treatment with 20 mM 4-aminopyridine. This effect of 4-aminopyridine depended on the presence of Ca++ in the incubation medium. The results are discussed in terms of facilitation by 4-aminopyridine of exocytotic transmitter release. We think that the increase of the empty synaptosomes was due to the exhaustion or inhibition of the synaptic vesicle recycling mechanism.
mesh_terms: D015761:4-Aminopyridine; D000631:Aminopyridines / Q000494:pharmacology*; D000818:Animals; D002540:Cerebral Cortex / Q000187:drug effects* / Q000648:ultrastructure; D004553:Electric Conductivity; D009411:Nerve Endings / Q000187:drug effects* / Q000648:ultrastructure; D051381:Rats; D011919:Rats, Inbred Strains; D013574:Synaptosomes / Q000648:ultrastructure
chemical_list: D000631:Aminopyridines; D015761:4-Aminopyridine