Evaluation of the effect of neuropeptides of the melanocortin family on stress-associated changes in the level of corticotropin-releasing hormone and corticosterone

Introduction. To date, the problem of studying the neuropeptide system of regulation of adaptive processes is relevant, since the stress reaction is a trigger for the occurrence of various diseases, in particular depression. Corticoliberin is considered as the main regulator of the hypothalamic-pituitary-adrenal axis, released in response to stress from the paraventricular nucleus of the hypothalamus, modulating the synthesis of adrenal hormones and further the processes of integration of neuroendocrine, autonomic and behavioral responses to stress.

The aim of the study was to evaluate the effect of neuropeptides on stress–induced changes in corticotropin-releasing hormone and corticosterone.

Material and methods. The experiment was carried out on male rats in the amount of 70 individuals, which were divided into several groups: a group of intact animals receiving an equiobject of water solution for intraperitoneally injection for 20 days (10 individuals), a group of animals receiving an equiobject of water solution for intraperitoneally injection in an experimentally created model of a depressive-like state for 20 days (20 individuals); experimental groups of animals who received intraperitoneally studied neuropeptide compounds Met-Glu-His-Phe-Pro-Gly-Pro and His-Phe-Arg-Trp-Pro-Gly-Pro at a dose of 100 mcg/kg/day for 20 days from day 1 of an experimentally created model of a depressive-like state. A depressive-like state was modeled by daily intermale confrontations for 20 days, as a result of which submissive and aggressive types of behavior were formed in rats. Neuroendocrine status was assessed by determining the level of key hormones of the hypothalamic-pituitary-adrenal axis (corticotropin-releasing hormone (corticoliberin) and corticosterone) in blood serum using enzyme immunoassay (ELISA).

Results. In conditions of stress-induced depression, a statistically significant increase in corticoliberin and corticosteroid in the blood of rats of both types of behavior was found, the difference in comparative aspect with the indicators of the control group, while exposure to neuropeptides against the background of stressful exposure contributed to a decrease in corticosterone levels by an average of 30% (p<0.05).

Conclusion. Thus, it was found that stress-induced depression is accompanied by hyperactivation of the hypothalamic-pituitary-adrenal axis, presumably due to a violation of the reverse inhibitory effects of endogenous glucocorticoids due to dysfunction of glucocorticoid receptors, which contributes to the development of a complex of manifestations of the main reactions, in particular, a decrease in the level of neurotrophic factors and the development of neurogenic inflammation. Neuropeptides of the glyproline series, in turn, showed the ability to reduce the activity of the hypothalamic-pituitary-adrenal axis by inhibiting the level of corticoliberin and corticosterone in conditions of stress-induced depression.