A synthetic, conformationally restricted analogue of L-glutamic acid which acts as a powerful neuronal excitant.

The activity of a synthetic compound, cis-1-aminocyclopentane-1,3-dicarboxylic acid, which possesses a conformationally very restricted molecule, has been compared with that of L-glutamic acid and a number of other compounds as a neuronal excitant. The new compound is about 10-fold more active than glutamate and its rigidity indicates that it reacts only with glutamate receptors and not with those responsive to aspartate.