Abstract— The intraperitoneal administration of 1-aminocyclopentane carboxylic acid, 1-aminocyclohex-ane carboxylic acid, l-aminocycloheptane carboxylic acid, 1-aminocyclooctane carboxylic acid, exo-2-aminobicyclo(2,2. l)heptane-2-carboxylic acid. endo-2-aminobicyclo(2,2.1)heptane-2-carboxylic acid. 2-aminobicyclo(2.2.2)octane-2-carboxylic acid and 2-aminobicyclo(3,2.l)octane-2-carboxylic acid to 18-day-old male rats selectively perturbed the levels of neutral amino acids in the cerebral cortex. While the effect of the above compounds was rather diversified and usually resulted in a reduction of amino acid levels. marked elevations of the levels of valine and isoleucine were also noted. 1-Aminocycloheptane and cyclooctane carboxylic acids were particularly noteworthy, in that they elicited a marked reduction of the levels of cortical phenylalanine.