Tetrapeptide L-alanyl-L-glutamyl-L-asparagyl-L-proline of the general formula L-Ala-L-Glu-Asp-L-Pro is proposed as a biologically active compound stimulating the functional activity of neurones. The application of L-Ala-L-Glu-L-Asp-L-Pro tetrapeptide in medicine is proposed for the preparation of a drug stimulating the functional activity of neurones. There is proposed a pharmacological agent, which contains as its active base an effective amount of L-Ala-L-Glu-L-Asp-L-Pro tetrapeptide for its salts of the amino acid group (acetate, hydrochloride, oxalate) or its salts of carboxyl groups (the salts of sodium, potassium, calcium, lithium, zinc, magnesium, and also the salts of organic and inorganic cations-ammonium, triethylammonium). The agent is proposed for parenteral, intranasal and oral administration. In accordance with the invention, the method of stimulating the functional activity of neurones consists in preventive and/or therapeutic administration to the patient of the pharmacological agent in doses 0.01 to 100 .mu.g/kg of the body weight at least one a day for a period necessary for attaining a therapeutic effect.