Compounds related to carnitine have been applied iontophoretically from five-barrelled micropipettes to neurons of the cerebral cortex of anesthetized cats. Both optically active and racemic mixtures of carnitine, acetyl carnitine, carnitine nitrile, and acetylcarnitylcholine had an excitatory action on cells excited by acetylcholine. The levorotatory forms were generally, but not invariably, stronger excitants than their enantiomers. Atropine administered intravenously blocked the action of all carnitines and acetylcholine. These derivatives (like ACh itself) had a depressant effect on some cells which were not excited by ACh.