It was shown, that photochemically induced thrombosis of blood vessels in prefrontal areas of the cortex lead to the formation of well-defined infarct zone. Bilateral prefrontal cortex injury impair acquisition of the Morris water-maze on postoperative days 20-24. Chronic treatment of brain-injuried rats with peptide semax, a synthetic analogue of ACTH(4-7), at a dose of 250 microg/kg (intranasal, once a day) during six days after photothrombosis resulted in restoration of spatial learning ability. The observed long-lasting antiamnesic effects of the semax are probably caused by its strong neuroprotective action, and ability to induce synthesis of nerotrophic factors.