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Natural melanocortins (MCs) have been used in the successful development of drugs with neuroprotective properties. Here, we studied the behavioral effects and molecular genetic mechanisms of two synthetic MC derivatives-ACTH(4–7)PGP (Semax) and ACTH(6–9)PGP under normal and acute restraint stress (ARS) conditions. Administration of Semax or ACTH(6–9)PGP (100 μg/kg) to rats 30 min before ARS attenuated ARS-induced behavioral alterations. Using high-throughput RNA sequencing (RNA-Seq), we identified 1359 differentially expressed genes (DEGs) in the hippocampus of vehicle-treated rats subjected to ARS, using a cutoff of >1.5 fold change and adjusted p-value (Padj) < 0.05, in samples collected 4.5 h after the ARS. Semax administration produced >1500 DEGs, whereas ACTH(6–9)PGP administration led to <400 DEGs at 4.5 h after ARS. Nevertheless, ~250 overlapping DEGs were identified, and expression of these DEGs was changed unidirectionally by both peptides under ARS conditions. Modulation of the expression of genes associated with biogenesis, translation of RNA, DNA replication, and immune and nervous system function was produced by both peptides. Furthermore, both peptides upregulated the expression levels of many genes that displayed decreased expression after ARS, and vice versa, the MC peptides downregulated the expression levels of genes that were upregulated by ARS. Consequently, the antistress action of MC peptides may be associated with a correction of gene expression patterns that are disrupted during ARS.

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This report describes studies cf the effects of the ACTH(4-10) analog Semax (MEHFPGP) on the behavior of white rats with lesions to the brain dopaminergic system induced by the neurotoxin MPTP. Neurotoxin was given as single i.p. doses of 25 mg/kg. Neurotoxin injections were shown to decrease movement activity and increase anxiety in the animals. Daily intranasal administration of Semax at a dose of 0.2 mg/kg decreased the severity of MPTP-induced behavioral disturbances. The protective activity of Semax in MPTP-induced lesions of the brain dopaminergic system may be associated with both its modulating effect on the dopaminergic system and the neurotrophic action of the peptide.