Stereoselective effects of two phencyclidine derivatives on N-methylaspartate excitation of spinal neurones in the cat and rat.

In pentobarbitone-anaesthetised cats and rats effects of stereoisomers of two methylated congeners of phencyclidine, GK4 and GK5, and (+)- and (-)-PCMP, were examined on the excitation of spinal neurones by electrophoretically administered excitatory amino acids and acetylcholine. GK5 and (+)-PCMP were more potent and selective antagonists of N-methylaspartate (NMA) than were GK4 and (-)-PCMP. None of these phencyclidine derivatives showed stereoselectivity in their effects on excitation of neurones by kainate, quisqualate and acetylcholine. The differences in potency between each pair of isomers as NMA antagonists correlates well with the differences reported in results from phencyclidine binding assays and behavioural tests.