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Abstract
The heptapeptide Semax (MEHFPGP) is an analog of the fragment ACTH(4-10) with long-lasting actions. The aim of the present work was to study the effects of Semax on learning ability and pain sensitivity in white rats given different doses via the intraperitoneal and intranasal routes. The nootropic effects of Semax were studied in a test based on the acquisition of a conditioned passive avoidance reaction to pain stimulation. Pain sensitivity was assessed in a hindpaw compression test. The results showed that i.p. Semax had nootropic and analgesic actions. Dose-response characteristics were different for these different effects. Intranasal Semax was more effective in improving learning in animals than i.p. Semax but had no effect on pain sensitivity. Our results provide evidence that different mechanisms and brain structures are involved in mediating the nootropic and analgesic effects of Semax.[PUBLICATION ABSTRACT]