Comparative study of analgesic potency of ACTH4-10 fragment and its analog semax.

The effects of ACTH4-10 fragment and its analog semax on nociception were examined on various animal models. ACTH4-10 in a dose of 0.5 mg/kg decreased nociception in rats during hindpaw compression test and in mice subjected to acetic acid writhing test. Lower doses of ACTH4-10 produced no analgesic effect. Semax (0.015-0.500 mg/kg) decreased pain sensitivity in all experimental models. Hence, the substitution of three C-terminal amino acid residues in ACTH4-10 for Pro-Gly-Pro sequence augmented the analgesic potency of the peptide after its peripheral injection.