[3H]D-serine labels strychnine-insensitive glycine recognition sites of rat central nervous system

In the central nervous system, glycine binds to two recognition sites; one of them (G2), associated with the glutamate receptor, is insensitive to strychnine. Strychnine-insensitive sites were predominant in the forebrain areas and bound D-serine and D-alanine better than the respective L stereoisomers. [3H]D-serine was a more selective radioligand than [3H]glycine for the strychnine-insensitive sites. In the forebrain, the binding of both ligands was inhibited by the putative G2 receptor antagonists, 7-chlorokynurenate and 3-amino-1-hydroxy-2-pyrrolidone, while in pons and in spinal cord only the latter drug was effective. This may indicate the heterogeneity of strychnine-insensitive glycine recognition sites.