EFFECT OF ACTH6-9-PRO-GLY-PRO PEPTIDE ON SPECTRAL PARAMETERS OF HEART RATE VARIABILITY IN WISTAR RATS DURING PHYSICAL EXERTION (PILOT STUDY)

Abstract

Objective: To study the effect of the ACTH6-9-Pro-Gly-Pro peptide (ACTH6-9-PGP) on the spectral parameters of heart rate variability (HRV) in Wistar rats during short-term exercise. Methods: The study involved 48 Wistar rats. ACTH6-9-PGP was once administered to the animals intraperitoneally at doses of 5, 50, and 500 µg/kg (3 groups of animals) in a volume of 1 ml/kg. Animals of the control group were injected with normal saline in an equivalent volume. Each group included 6 males and 6 females. HRV indicators were recorded using the Physiobelt 2.5.1 complex (Neurobotics, Russia). HRV analysis was performed by spectral parameters: total power of the spectrum of HRV (TP), the total power of the high-frequency component (HF) (ms2 , %), the total power of the lowfrequency component (LF) (ms2 , %), the total power of the very low-frequency component (VLF) (ms2 , %), LF/HF ratio (LF/HF), index of centralization (IC). The cardio signal was recorded 4 times: 1 – after adaptation to the device; 2 – 15 minutes after the injection of the peptide; 3 – after physical activity (2-minute treadmill run), and 4 – after a 15-minute rest. Results: An analysis of the initial values of the HRV indicators made it possible to establish a shift in the spectral characteristics toward the VLF component in the studied groups. Physical activity in the control group caused an increase in the power of HF, LF, and VLF, however, their ratio (VLF>LF>HF) did not change at all stages of the study. A single intraperitoneal injection of the ACTH6-9-PGP peptide at a dose of 5 μg/kg stabilized the HRV parameters at the initial level. The administration of the peptide at a dose of 50 μg/kg and moderate physical activity were accompanied by an increase in the power of HF and LF compared to the initial level. The percentage of frequency components after the exercise was LF>VLF>HF, and in the recovery period, it became VLF>LF>HF. After the administration of the peptide at a dose of 500 μg/kg, an increase in HF and LF, and a redistribution of the frequency components toward LF>HF>VLF were noted. During the recovery period, a decrease in HF, restoration of the percentage of frequency indicators VLF>LF>HF, and an increase in LF/HF and IC were found. Conclusion: A study of the effects of the ACTH6-9-PGP peptide on HRV in Wistar rats showed that a single intraperitoneal injection at a dose of 5 µg/kg promotes adaptation of laboratory animals to physical activity due to the activation of suprasegmental structures, and at doses of 50 and 500 µg/kg – predominant activation of the peripheral segments of the sympathetic and parasympathetic autonomic systems. Keywords: ACTH6-9-Pro-Gly-Pro, heart rate variability, physical activity, Wistar rats, spectral parameters.