Synthesis of 1,4,7,8,9,10-hexahydro-9-methyl-6-nitropyrido[3,4-f]-quinoxaline-2,3-dione and related quinoxalinediones: characterization of .alpha.-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (and N-methyl-D-aspartate) receptor and anticonvulsant activity

Abstract

Four related series of substituted quinoxalinediones containing angular fused-piperidine rings have been synthesized as alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor antagonists with potential as neuroprotective agents, primarily for acute therapy immediately following a stroke. The compounds were tested for their affinity to the AMPA, kainate, and strychnine-insensitive glycine receptor sites. In AMPA binding, the most potent compound was 27a (PNQX, IC50 = 63 nM), with affinity comparable to the literature standard 1 (NBQX, IC50 = 52 nM). Other 6-nitro analogs from the 9-aza series had comparable affinity at the AMPA receptor, as did 6-nitro-8-aza derivatives such as 13a (iPNQX, IC50 = 290 nM). The receptor binding profile of 27a differed from that of 1 in that 27a possessed significant affinity at the glycine site of the N-methyl-D-aspartate (NMDA) receptor, whereas 1 was essentially inactive. Three compounds, 26c, 26d, and 26e, demonstrated moderate selectivity for kainate relative to AMPA receptors. Selected analogs reported herein as well as in the literature were superimposed to generate an AMPA pharmacophore model, and 6-substituted compounds from the PNQX and iPNQX series were combined and analyzed via quantitative structure-activity relationship techniques. Compounds with high affinity at non-NMDA receptors were further characterized in functional assays in neuronal cell culture and in a cortical wedge preparation. Both 1 and 27a showed comparable effectiveness in an AMPA- and kainate-induced excitoxicity assay. Both inhibited AMPA-induced depolarizations in the cortical wedge. However, 27a also inhibited spontaneous epileptiform discharges in the cortical wedge (reversed by glycine), while 1 was ineffective. The combination of AMPA and NMDA antagonist activity may contribute to the 30-fold difference in potency between 27a and 1 in the maximal electroshock convulsant assay in mice. The significant in vivo potency of 27a suggests that it has potential clinical utility.

Glutamate Receptor Ion Channels: Activators and Inhibitors

“…Progress has been made in the design of both quinoxalinediones and closely related analogues (BIGGE et al 1995;VERDOON et at. 1994;WILDING and HUETTNER 1996) and notably decahydroisoquinolines as kainate receptor antagonists (BLEISCH et al 1997;CLARKE et al 1997;SIMMONS et al 1998).…”

“…2) series of compounds that a bromo substituent in the 6-position and a bulky N-alkyl substituent on the piperidine moiety (see compound VIII, Fig. 2) leads to selectivity for kainate receptors suggesting that hydrophobic interactions are important for kainate receptor binding (BIGGE et al 1995).…”

“…fTaken from TURSKI et al (1996). g NBQX is reference substance for PNQX; ICso values taken from BIGGE et al (1995). hICso value taken from WATJEN et al (1994).…”

“…2) has the advantage of good aqueous solubility (1.68 gil) at physiological pH. A series of novel quinoxalinediones have been developed by combining the fused cyclic amine structure of NS257 and the quinoxalinedione ring of NBQX (BIGGE et al 1995). One of these, 1,4,7,8,9,lO-hexahydro-9-methyl-6-nitropyrido[3,4-f]-quinoxaline-2,3-dione (PNQX, Fig.…”

The Neuroprotective Effect of the Novel AMPA Receptor Antagonist PD152247 (PNQX) in Temporary Focal Ischemia in the Rat

“…24 Recently, a novel quinoxalinedione PD152247 (PNQX) was discovered. 25 PNQX binds with high affinity to the AMPA receptor (IC 50 , 90 nmol/L) and with modest affinity to the kainate receptor and the glycine site of the NMDA receptor. PNQX antagonizes effects of AMPA in AMPAinduced cytotoxicity in primary neuronal cultures and protects against AMPA and maximal electroshock-induced seizures in mice (unpublished data, Boxer and Probert, 1999).…”