Effects of Fragment ACTH15-18 and Its Analog ACTH15-18Pro-Gly-Pro on the Sequelae of Acute Stress.

Tetrapeptide KKRR, corresponding to the ACTH_15-18 sequence, is the shortest fragment with high-affinity binding with the ACTH receptor; it does not activate this receptor and prevents the whole hormone molecule from binding to it, and thus exhibits the properties of an ACTH receptor antagonist. The aim of the present work was to study the effects of peptide ACTH_15-18 (KKRR) and its analog ACTH_15-18PGP on behavior in Wistar rats in normal conditions and after acute stress produced by inescapable electrical foot shock. The peptides studied here did not affect the anxiety levels in white rats in normal conditions. Prior administration of ACTH_15-18 (250 μg/kg) and its analog ACTH_15-18PGP (50 and 250 μg/kg) decreased anxiety and corticosterone release in rats which had received a acute electrical foot shock stress. The extent and duration of the anti-stress effects of ACTH_15-18PGP were significantly greater than the extent and duration of the effects of its natural prototype. [ABSTRACT FROM AUTHOR]