Synthetic corticotropins and the GABA-receptor system: Direct and delayed effects.

The central effectors of the stress system are greatly interconnected and include, among others, a large group of peptides derived from proopiomelanocortin. In addition to natural corticotropins, a number of artificial molecules that contain some ACTH fragments in their structure are also referred to members of this family. Some of them possess a wide range of biological activity. The molecular mechanism underlying the biological activity of such peptides is partly based on allosteric modulation of various receptors. We analyzed the ability of some biologically active synthetic corticotropins (ACTH(4-7)PGP, ACTH(6-9)PGP, ACTH(7-10)PGP), and glyproline PGPL to affect the GABA-receptor system of rat brain. The effects of the peptides were studied in the isolated plasma membranes of brain cells, as well as after systemic peptide administration in the rat model of acute restraint stress. The delayed effect of stress or preadministration of each of the studied peptides on [3 H]GABA binding was different for its high- and low-affinity-specific sites. The studied peptides individually affected the binding of [3 H]GABA in their own way. Acute restraint stress caused a decrease in [3 H]GABA binding at its low-affine site and did not affected the high-affine site. Preliminary peptide administration did not influence this effect of stress.

Antistress Action of Melanocortin Derivatives Associated with Correction of Gene Expression Patterns in the Hippocampus of Male Rats Following Acute Stress.

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.

Neuroleptic properties of the ion-channel-forming peptaibol zervamicin: locomotor activity and behavioral effects.

Zervamicins IIA and IIB are members of the peptaibol family of peptide antibiotics. They are produced by the fungus Emericellopsis salmosynnemata. Peptaibols are known to be of potential usefulness for chemotherapeutic applications, as are other secondary fungal metabolites. Previously, we have found zervamicins to decrease spontaneous locomotor activity in mice, suggesting their neurotropic properties on an equal footing with antimicrobial activity. The current study deals with behavioral effects of zervamicins IIA and IIB in mice. According to our results, both zervamicins induce a reliable decrease in locomotion and exploratory activity measured in the hole-board test. The behavioral effects of zervamicin IIA become apparent at lower dosages (0.05-2.0 mg/kg) as compared with zervamicin IIB (0.5-12.0 mg/kg). The experiments on behavioral effects in the elevated plus maze test showed that both zervamicins caused a reliable decrease in the number of head-dippings, open-arm entries, and rearings. The observed behavioral effects may be rather associated with a decrease in the exploratory activity than with anxiety-related responses in mice. Zervamicins induced depression-like behavior of experimental animals in the forced-swim test. Both peptaibols reduce physical endurance and change motor coordination of experimental animals in the bar-holding test. Taken together, the data obtained clearly indicate that both zervamicins possess neuroleptic activity.