Epileptiform activity induced by 4-aminopyridine in guinea-pig and rat neocortices.
Extracellular field recordings were performed in guinea-pig and rat neocortical slice preparations maintained in vitro. Bath application of the convulsant drug 4-aminopyridine (4-AP, 100 microM) induced spontaneous epileptiform potentials in 80% of the guinea-pig neocortical slices and only in 6% of the neocortical slices from rat. In both species spontaneous epileptiform activity consisted of a 4-16 s long ictal-like discharge that recurred with a frequency range of 0.01-0.02 Hz. In rat neocortical slices stimulus-induced responses resembled the spontaneous occurring epileptiform events. Ictal-like discharges in guinea-pig neocortical slices were blocked by the N-methyl-D-aspartate (NMDA) receptor antagonist 3-((+/-)-2-carboxypiperazine-4-yl)propyl-1-phosphonic acid (5 microM), while those in the rat disappeared during perfusion with the non-NMDA excitatory amino acid receptor antagonist 6-cyano-7-nitroquinoxaline-2,3-dione (1-3 microM). These results indicate that the neocortex of guinea-pig has a higher propensity to generate 4-AP-induced spontaneous epileptiform activity than that of rat. Furthermore the epileptiform activity in these two species requires a different involvement of excitatory amino acid receptors.
Mattia
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Montreal Neurological Institute, Qué., Canada.
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D015761:4-Aminopyridine; D018750:6-Cyano-7-nitroquinoxaline-2,3-dione; D000818:Animals; D000927:Anticonvulsants / Q000494:pharmacology; D002540:Cerebral Cortex / Q000187:drug effects / Q000503:physiopathology*; D004558:Electric Stimulation; D004594:Electrophysiology; D004827:Epilepsy / Q000139:chemically induced* / Q000503:physiopathology; D006168:Guinea Pigs; D066298:In Vitro Techniques; D010879:Piperazines / Q000494:pharmacology; D011810:Quinoxalines / Q000494:pharmacology; D051381:Rats; D016194:Receptors, N-Methyl-D-Aspartate / Q000037:antagonists & inhibitors
D000927:Anticonvulsants; D010879:Piperazines; D011810:Quinoxalines; D016194:Receptors, N-Methyl-D-Aspartate; D018750:6-Cyano-7-nitroquinoxaline-2,3-dione; C050592:3-(2-carboxypiperazin-4-yl)propyl-1-phosphonic acid; D015761:4-Aminopyridine