Abstract: This invention is characterized by a brain function improving preparation containing theanine not less than 50 &mgr;M. It was confirmed that theanine could increase intracellular Ca2+ concentration by acting on NMDA receptors even at a low dose of about 50 &mgr;M. Thus, the brain function improving preparation of this invention was shown to be capable of causing plastic change in neurons or neural circuit. Since theanine has been approved as a food additive and being consumed daily, its safety has no problem. Moreover, theanine passes the blood-brain barrier relatively easily and, thus, it is effective as an oral preparation.

Abstract: Disclosed is an agent for curing neuronal diseases caused by disorders of peripheral nervous system or central nervous system, which comprises a 2-acylaminopropanol compound of the formula: ##STR1## wherein R.sup.1 represents a phenyl group or cyclohexyl group each of which may be substituted by 1 to 3 same or different substituents selected from the group consisting of alkyl, alkoxy, hydroxy and nitro, or represents an alkyl group, and n represents an integer of 0 to 16,or a pharmaceutically acceptable salt thereof as an effective ingredient.