In vivo pharmacology of BIIR 561 CL, a novel combined antagonist of AMPA receptors and voltage-dependent Na+ channels

1 Glutamate receptors of the alpha -amino-3-hydroxy-5-methyl-4-isoxazolepro pionic acid (AMPA) subtype and voltage-gated Na+ channels are associated wi th diseases of the central nervous system characterized by neuronal over-ex citation as in epilepsy or cerebral ischaemia. In animal models, AMPA recep tor antagonists and Na+ channel blockers provide protection in these condit ions. 2 Dimethyl-{2-[2-(3 -phenyl-[1,2,4]oxadiazol-5-yl)-phenoxyl]-ethyl}-amine h ydrochloride (BIIR 561 CL) combines both, AMPA receptor-and Na+ channel blo cking properties in one molecule. Here, BIIR 561 CL was investigated in viv o. 3 BIIR 561 CL protected mice against AMPA-induced toxicity with an ED50 val ue of 4.5 mg kg(-1) following subcutaneous (s.c.) administration. A 0.1% so lution of BIIR 561 CL provided local anaesthesia in the corneal reflex test in rabbits. In mice, the compound prevented tonic seizures in the maximal electroshock (MES) model with an ED50 value of 3.0 mg kg(-1) s.c. In amygda la-kindled rats, BIIR 561 CL inhibited seizures at doses of 3 and 11 mg kg( -1) following intraperitoneal (i.p.) injection. 4 The data show that the combination of blocking AMPA receptor- and voltage -gated Na+ channels in one molecule induces effective protection in animal models of neuronal over-excitation.