Improvements in or relating to excitatory amino acid receptor antagonists

Excitatory amino acid receptor antagonists and methods for the use thereof are disclosed. The antagonists include compounds having the preferred formula: or in which: each of A1, A2 and A3 is independently either C or N, except that at least one of A1, A2 and A3 is N; one of A4 and A5 is C and the other is N; each R1 and R2 is independently hydrogen, halogen, CN, NO2, alkyl, aromatic, azido or CF3; and R3 is hydrogen, alkyl, aromatic or CF3. Also included are the tautomers thereof, and the pharmaceutically acceptable salts of (III) and (IV) and the tautomers thereof. These compounds are useful as EAA antagonists for blocking one or more EAA receptors, for reducing EAA phosphoinositide hydrolysis, as neuroprotective agents, and in the treatment of various neurological disorders associated with EAA receptors.