Sigma receptor ligands (+)-SKF10,047 and SA4503 improve dizocilpine-induced spatial memory deficits in rats

This study examined the effects of the sigma receptor ligands (+)-N-allylnormetazocine ((+)-SKF10,047) and 1-(3,4-dimethoxyphenethyl)-4-(3-phenylpropyl)piperazine dihydrochloride (SA4503) on dizocilpine-induced impairment of working and reference memory in a radial arm maze task in rats. Dizocilpine, a non-competitive NMDA receptor antagonist, significantly impaired both reference and working memory, an effect which was accompanied by ataxia and impairment of food intake. The dizocilpine-induced impairment of reference memory was dose-dependently attenuated by (+)-SKF10,047 and SA4503. SA4503 also attenuated the dizocilpine-induced working memory impairment, although (+)-SKF10,047 had no effect. Neither sigma receptor ligand affected the behavioral symptoms such as ataxia and impairment of food intake induced by dizocilpine. The ameliorating effects of both (+)-SKF10,047 and SA4503 on dizocilpine-induced spatial memory impairment were completely antagonized by a sigma1 receptor antagonist N,N-dipropyl-2-[4-methoxy-3-(2-phenylethoxy)phenyl]-ethylamine-mon ohydrochloride. These results suggest that the interaction of sigma1 receptors with NMDA receptors modulates spatial memory in rats.