title: Differential heart rate variability and physiological responses associated with accumulated short- and long-term stress in rodents.
abstract: In this study, we tested the hypothesis that chronic stress has cumulative effects over time on heart rate variability (HRV) and physiological responses in a rodent model of chronic mild stress. Rats were exposed to either short-term (2weeks) or long-term (4weeks) stress, followed by a 1-week recovery period. Controls were normally housed rats that did not undergo the stress procedure. For electrocardiogram recordings, transmitters were implanted in all rats 10days before the onset of the experiment to allow recovery from surgery. To investigate physiological responses, body weight, temperature, sucrose preference, and serum corticosterone levels were measured weekly. Rats exposed to both short- and long-term stress showed significant reductions in body weight, which did not normalize after the recovery period. A significant difference was observed between short- and long-term stress groups in serum corticosterone levels, with long-term stress significantly increasing serum corticosterone levels, which remained elevated after the recovery period (P<0.05). HRV analysis indicated that long-term stress significantly decreased time-domain indexes, whereas significantly increased frequency-domain indexes were observed in the low-frequency range (0.1-1Hz). These results may represent dysfunction in parasympathetic/vagal modulation with hyperactivation of the sympathetic nervous system after long-term exposures to stress. In addition, prolonged Q-to-T wave (QT) intervals were observed in rats exposed to long-term stress, which did not return to baseline levels after the recovery period. These findings are consistent with the view that chronic stress is associated with cardiac autonomic disorders and emphasize the importance of monitoring stress in our daily life since the effects of even mild stress may be cumulative.
authors.affiliation: Biomedical Research Institute, Korea Institute of Science and Technology, Hwarangno 14-gil 5, Seongbuk-gu, Seoul 02792, South Korea; School of Mechanical Engineering, Korea University, 145 Anam-ro, Seongbuk-gu, Seoul 02841, South Korea.
authors.forename: Sunghee E
authors.initials: SE
authors.lastname: Park
authors.affiliation: Biomedical Research Institute, Korea Institute of Science and Technology, Hwarangno 14-gil 5, Seongbuk-gu, Seoul 02792, South Korea; Department of Bio-convergence Engineering, Korea University, 145 Anam-ro, Seongbuk-gu, Seoul 02841, South Korea.
authors.forename: Dajeong
authors.initials: D
authors.lastname: Park
authors.affiliation: Biomedical Research Institute, Korea Institute of Science and Technology, Hwarangno 14-gil 5, Seongbuk-gu, Seoul 02792, South Korea; School of Electrical and Electronic Engineering, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul 03722, South Korea.
authors.forename: Kang-Il
authors.initials: KI
authors.lastname: Song
authors.affiliation: Department of Bio-convergence Engineering, Korea University, 145 Anam-ro, Seongbuk-gu, Seoul 02841, South Korea.
authors.forename: Joon-Kyung
authors.initials: JK
authors.lastname: Seong
authors.affiliation: School of Mechanical Engineering, Korea University, 145 Anam-ro, Seongbuk-gu, Seoul 02841, South Korea.
authors.forename: Seok
authors.initials: S
authors.lastname: Chung
authors.affiliation: Biomedical Research Institute, Korea Institute of Science and Technology, Hwarangno 14-gil 5, Seongbuk-gu, Seoul 02792, South Korea; Department of Biomedical Engineering, Korea University of Science and Technology, Hwarangno 14-gil 5, Seongbuk-gu, Seoul 02792, South Korea. Electronic address: iyoun@kist.re.kr.
authors.forename: Inchan
authors.initials: I
authors.lastname: Youn
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D001831:Body Temperature; D001835:Body Weight / Q000502:physiology; D003345:Corticosterone / Q000097:blood; D004562:Electrocardiography; D005508:Food Deprivation / Q000502:physiology; D005518:Food Preferences; D006339:Heart Rate / Q000502:physiology*; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley; D013312:Stress, Physiological / Q000502:physiology*; D013686:Telemetry; D013997:Time Factors
chemical_list: D003345:Corticosterone
keywords: Electrocardiogram; Heart rate variability; Serum corticosterone; Stress