Effects of YM90K, a selective AMPA receptor antagonist, on amygdala-kindling and long-term hippocampal potentiation in the rat

To investigate the role of α-amino-3-hydroxy-5-methyl-isoxazole-4-propionic acid (AMPA) type glutamate receptors in epileptic seizures, we examined the antiepileptogenic and anticonvulsant effects of YM90K [6-(1H-imidazol-1-yl)-7-nitro-2,3-(1H,4H)-quinoxalinedione hydrochloride], a potent and selective new AMPA receptor antagonist, in the rat amygdala-kindling model of epilepsy. Pretreatment with YM90K (7.5-30 mg/kg i.p.) markedly retarded the evolution of kindling. Once kindling was established, administration of YM90K (7.5-30 mg/kg i.p.) significantly and dose-dependently suppressed fully kindled seizures. The maximal effects were observed 15-30 min after injection. When the intensity of electrical stimulation was increased to twice the generalized seizure-triggering threshold, the anticonvulsant effects of YM90K were reversed, suggesting that they were due to elevation of the generalized seizure-triggering threshold. Furthermore, an anticonvulsant dose (15 mg/kg) of YM90K affected neither field potentials nor long-term potentiation in the hippocampus in vivo. These results indicate that AMPA receptors play an important role in the seizure expression mechanism and the development of kindling-induced epileptogenesis, and suggest the possible clinical usefulness of AMPA receptor antagonists as antiepileptic drugs.