6-(1h-imidazol-1-yl)-7-nitro-2-3(1h-4h)-quinoxalinedione and Seizures

As part of a program aimed at discovering orally active 2-amino-3-(3-hydroxy-5-methyl-4-isoxazolyl)propionic acid (AMPA) receptor antagonists, we screened our compound library and identified 2-[allyl(4-methylphenyl)amino]-4H-pyrido[3,2-e][1,3]thiazin-4-one (7) as a lead compound that inhibited kainate-induced neurotoxicity mediated by AMPA receptors in rat hippocampal cultures. Structure-activity relationship studies of a series of 2-amino-4H-pyrido[3,2-e][1,3]thiazin-4-one derivatives revealed that substituents on the phenyl ring attached to the 2-amino group and the 4H-pyrido[3,2-e][1,3]thiazin-4-one ring system play an important role in inhibitory activity against kainate-induced neurotoxicity. Several analogs bearing a phenyl group with a 4-substituent or five- or six-membered ring fused at the 3,4-positions exhibited potent inhibitory activity against kainate-induced neurotoxicity. Further, some of these compounds exhibited significant suppression of maximal electroshock seizure in mice following oral administration. Of these compounds, 2-[(4-chlorophenyl)(methyl)amino]-4H-pyrido[3,2-e][1,3]thiazin-4-one (16i) (YM928) demonstrated the most potent inhibitory effect with an ED50 value of 7.4mg/kg.

Topics: Animals; Anticonvulsants; Antinematodal Agents; Cells, Cultured; Electroshock; Hippocampus; Kainic Acid; Mice; Neurons; Pyridines; Rats; Receptors, AMPA; Seizures; Structure-Activity Relationship; Thiazines

A novel series of readily water soluble 8-methylureido-4,5-dihydro-4-oxo-10H-imidazo[1,2-a]indeno[1,2-e]++ +pyrazines were synthesized. The -10-yl acetic acid ((+)-3) and -10-carboxylidene (4) derivatives exhibit potent affinities (IC50=4 and 19 nM, respectively) and antagonist properties (IC50 = 2 and 3 nM, respectively) at the ionotropic AMPA receptor. These compounds also display anticonvulsant properties against both electrically and sound-induced convulsions in mice after ip, sc and iv administration with ED50 values between 0.9 and 11 mg/kg, thus suggesting adequate brain penetration.

Topics: Animals; Anticonvulsants; Excitatory Amino Acid Antagonists; Isoquinolines; Mice; Oocytes; Pyrazines; Quinoxalines; Receptors, AMPA; Receptors, N-Methyl-D-Aspartate; Seizures; Tetrazoles; Xenopus laevis

In this study, we examined the acute anticonvulsant spectrum of (1) dizocilpine (0.03-3 mg/kg), CGS 19755 (1-10 mg/kg), and 7-chlorokynurenic acid (1-100 nmol) (NMDA receptor/ionophore complex antagonists); (2) muscimol (0.1-10 nmol; direct GABA(A) agonist); (3) YM90K (3-10 mg/kg; AMPA receptor antagonist); and (4) diazepam (2 and 5 mg/kg) and carbamazepine (5 and 20 mg/kg), two standard anticonvulsants, using the partially-kindled hippocampal model for epileptic seizures in freely moving rats. The anticonvulsant effect of these compounds were assessed by determining (1) the afterdischarge (AD), which is indicative of the severity of the seizure and related to seizure maintenance, and (2) the pulse number threshold (PNT), which is indicative of the seizure threshold or initiation. In addition, ataxia, a measure of CNS dysfunction, was assessed for each compound. Overall, our results indicated that the anticonvulsant compounds examined could be classified into three categories based on effects on the AD and PNT: (1) elevation of PNT (carbamazepine, dizocilpine, CGS 19755 and 7-chlorokynurenic acid); (2) reduction of AD (diazepam and muscimol); and (3) mixed action, i.e., increased PNT and decreased AD (YM90K). Behavioral data indicated that all compounds, except carbamazepine, produced a dose- or concentration-dependent ataxia. Overall, our results suggest that NMDA receptors play a role in seizure initiation, whereas the GABA(A) receptors appear to be involved in seizure maintenance and AMPA receptors may be involved in both phenomena.

Topics: Animals; Anticonvulsants; Ataxia; Carbamazepine; Diazepam; Dizocilpine Maleate; Excitatory Amino Acid Antagonists; GABA Agonists; Hippocampus; Kynurenic Acid; Male; Muscimol; Pipecolic Acids; Quinoxalines; Rats; Rats, Wistar; Seizures

To investigate the effects of a new non-NMDA antagonist on the trisynaptic pathways in the hippocampus, the author examined the kainate(KA)-induced generalized seizures in rats. A novel non-NMDA antagonist, YM90K, showed the blockade of the Schaffer collaterals in a 2-deoxyglucose study (2-DG) and that the CA1-2 pyramidal cells of the hippocampus were preserved seven days after the KA injections. On the other hand, the control and MK-801 (NMDA-antagonist) treated rats did not depress the Schaffer collaterals and showed persistent hypermetabolism of glucose in the CA1 pyramidal cell layer, where neurons were not preserved seven days later. 2-DG was useful to reveal the effects of a non-NMDA antagonist on the KA-induced generalized seizures. This suggests that YM90K is a potent non-NMDA antagonist and that it has a neuroprotective effect in rats.

Topics: Animals; Anticonvulsants; Brain; Dizocilpine Maleate; Glucose; Hippocampus; Kainic Acid; Male; N-Methylaspartate; Quinoxalines; Rats; Rats, Sprague-Dawley; Seizures

To investigate the effects of a new nonNMDA antagonist on the trisynaptic pathways in the hippocampus, the author examined kainate(KA)-induced generalized seizures in rats. A novel nonNMDA antagonist, YM90K, showed the blockade of the Schaffer collaterals in 2-deoxyglucose study (2-DG) and that the CA1-2 pyramidal cells of the hippocampus were preserved seven days after the KA injections. On the other hand, the control and MK-801 (NMDA-antagonist) treated rats did not depress the Schaffer collaterals and showed persistent hypermetabolism of glucose in the CA1 pyramidal cell layer, where neurons were not preserved seven days later. 2-DG was useful to reveal the effects of nonNMDA antagonist on the KA-induced generalized seizures. This suggests that YM90K is a potent nonNMDA antagonist and that it has a neuroprotective effect in rats.

Topics: Animals; Autoradiography; Brain; Deoxyglucose; Excitatory Amino Acid Antagonists; Glucose; Hippocampus; Kainic Acid; Male; Nerve Net; Neuroprotective Agents; Pyramidal Cells; Quinoxalines; Rats; Rats, Sprague-Dawley; Seizures

We investigated the pharmacological properties and neuroprotective actions of a novel alpha-amino-3-hydroxy-5-methylisoxazole-y-propionate (AMPA)/kainate receptor antagonist, [6-(1H-imidazol-1-yl)-7-nitro-2,3-(1H,4H)-quinoxalinedione hydrochloride (YM90K); formerly YM900], in comparison with those of 2,3-dihydroxy-6-nitro-7-sulfamoyl-benzo(f)quinoxaline (NBQX). YM90K selectively displaced [3H]-AMPA binding (Ki = 0.084 microM) and was less potent in inhibiting [3H]-kainate (Ki = 2.2 microM), [3H]-L-glutamate (N-methyl-D-aspartate-sensitive site; Ki > 100 microM) and [3H]-glycine (strychnine-insensitive site; Ki = 37 microM) binding to rat brain membranes. YM90K co-injected with AMPA or kainate into the rat striatum protected cholinergic neurons against AMPA- or kainate-induced neurotoxicity. YM90K showed potent suppressive activity against audiogenic seizure in DBA/2 mice; ED50 values of YM90K and NBQX against tonic seizure were 2.54 and 7.17 mg/kg (i.p.), respectively. The duration of the anticonvulsant effects of YM90K and NBQX was 30 min, indicating that both compounds possess short action. In a global ischemia model, YM90K (15 mg/kg i.p. x 3), NBQX (30 mg/kg i.p. x 3) and CNQX (60 mg/kg i.p. x 3) significantly prevented the delayed neuronal death in the hippocampal CA1 region in Mongolian gerbils when administered 1 h after 5-min ischemia. In addition, the therapeutic time window for the neuroprotective effect of YM90K (30 mg/kg i.p. x 3) was 6 h. In a focal ischemia model, YM90K (30 mg/kg i.v. bolus+10 mg/kg/h for 4 h) reduced the volume of ischemic damage in the cerebral cortex in F344 rats. Thus, YM90K was shown to be a potent and selective antagonist for AMPA/kainate receptors in vitro and in vivo. This compound may provide a therapeutic effect in various neurodegenerative disorders such as ischemic stroke in which glutamate neurotoxicity is thought to play a critical role in neuronal damage.

Topics: Animals; Anticonvulsants; Brain Ischemia; Cerebral Infarction; Corpus Striatum; Gerbillinae; Ischemia; Male; Mice; Mice, Inbred DBA; Quinoxalines; Radioligand Assay; Rats; Rats, Inbred F344; Rats, Wistar; Receptors, AMPA; Receptors, Kainic Acid; Seizures

A novel series of quinoxalinediones possessing imidazolyl and related heteroaromatic substituents was synthesized and evaluated for their activity to inhibit [3H]AMPA binding from rat whole brain. From the structure-activity relationships, it was found that the 1H-imidazol-1-yl moiety could function as a bioisostere for the cyano and nitro groups, and that 6-(1H-imidazol-1-yl)-7-nitro-2,3(1H,4H)-quinoxalinedione (11) showed the most potent activity for the AMPA receptor. Compound 11 was evaluated for selectivity versus other excitatory amino acid receptors, and its action against AMPA at its receptor in the rat striatum was characterized. These data showed that compound 11 was a selective antagonist for the AMPA receptor with a Ki value of 0.084 microM, being approximately equipotent with 2,3-dihydro-6-nitro-7-sulfamoylbenzo(f)quinoxaline (3) (NBQX; Ki = 0.060 microM). Compound 11 was also found to give protection against sound-induced seizure on DBA/2 mice at the minimum effective dose of 3 mg/kg ip (3; 10 mg/kg ip).

Topics: Acoustic Stimulation; Animals; Anticonvulsants; Binding Sites; Brain; Imidazoles; Male; Mice; Mice, Inbred DBA; Quinoxalines; Rats; Rats, Wistar; Receptors, AMPA; Receptors, N-Methyl-D-Aspartate; Seizures; Structure-Activity Relationship