title: K(+)-channel openers suppress epileptiform activities induced by 4-aminopyridine in cultured rat hippocampal neurons.
abstract: K(+) channels are key modulators of neuronal excitability, and mutations in certain types of these channels are known to cause epileptic seizures. Activation of K(+) channels is reported to suppress epileptic discharge; however, the types of K(+)-channel openers that are most effective as anti-epileptic agents are not well understood. We established a quantitative fluorescence assay using the Na(+) indicator sodium-binding benzofuran isophthalate (SBFI) for evaluation of various compounds on epileptiform activities induced by 4-aminopyridine (4-AP) in cultured rat hippocampal neurons. Among the K(+)-channel openers, the K(V)7.2/K(V)7.3-channel openers retigabine and flupirtine and K(Ca)2-channel openers NS309, DCEBIO, and 1-EBIO showed potent anti-epileptic effects similar to conventional antiepileptic drugs (AEDs). In contrast, the K(Ca)1.1-channel openers NS1619, isopimaric acid, and chlorzoxazone demonstrated moderate inhibition. The K(ir)6-channel openers minoxidil, cromakalim, and pinacidil did not show anti-epileptic effects. We concluded that K(V)7.2/K(V)7.3, K(Ca)2, and, to some extent, K(Ca)1.1-channel openers, but not K(ir)6-channel openers, suppress 4-AP-induced epileptiform activities in hippocampal neurons. These results suggest that the K(+)-channel openers for this category of K(+) channels might have therapeutic potential as new classes of antiepileptic drugs.
authors.affiliation: Department of Anesthesiology, Graduate School of Comprehensive Human Sciences, University of Tsukuba, Japan. k8-kobayashi@hhc.eisai.co.jp
authors.forename: Kiyoaki
authors.initials: K
authors.lastname: Kobayashi
authors.forename: Yukio
authors.initials: Y
authors.lastname: Nishizawa
authors.forename: Kohei
authors.initials: K
authors.lastname: Sawada
authors.forename: Hiroo
authors.initials: H
authors.lastname: Ogura
authors.forename: Masayuki
authors.initials: M
authors.lastname: Miyabe
mesh_terms: D015761:4-Aminopyridine; D000818:Animals; D000927:Anticonvulsants / Q000494:pharmacology*; D001572:Benzofurans; D002478:Cells, Cultured; D004827:Epilepsy / Q000188:drug therapy* / Q000503:physiopathology; D004988:Ethers, Cyclic; D005453:Fluorescence; D005456:Fluorescent Dyes; D006624:Hippocampus / Q000166:cytology / Q000187:drug effects; D009474:Neurons / Q000187:drug effects* / Q000378:metabolism; D015221:Potassium Channels / Q000187:drug effects* / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar
chemical_list: D000927:Anticonvulsants; D001572:Benzofurans; D004988:Ethers, Cyclic; D005456:Fluorescent Dyes; D015221:Potassium Channels; C061665:sodium-binding benzofuran isophthalate; D015761:4-Aminopyridine