Maladaptive alteration of fear response induced by complex trauma in adult male rats
Junhyung Kim 1, 2, Minkyung Park 2, 3, Jung Jin Ha 4, Chiheon Lee 1, 2, June-Seek Choi 5, Chul Hoon Kim 6, Jeong-Ho Seok 1, 2, 3*
1Department of Psychiatry, Yonsei University College of Medicine, Seoul, Korea, 2Institute of Behavioral Science in Medicine, Yonsei University College of Medicine, Seoul, Korea, 3Brain Korea 21 PLUS Project for Medical Science, Yonsei University College of Medicine, Seoul, Korea, 4Department of Psychology, Yonsei University, Seoul, Korea, 5Department of Psychology, Korea University, Seoul, Korea, 6Department of Pharmacology, Yonsei University College of Medicine, Seoul, Korea
Received: February 4, 2020; Revised: April 10, 2020; Accepted: April 10, 2020; Published online: April 10, 2020.
© The Korean College of Neuropsychopharmacology. All rights reserved.

Abstract
Objective: Despite the etiological significance of complex developmental trauma in adult personality disorders and treatment-resistant depression, neurobiological studies have been rare due to the lack of useful animal models. As a first step, we devised an animal model to investigate the effects of multiple trauma-like stress during different developmental periods. Methods: Twenty-one male Sprague-Dawley rats were classified into 3 groups based on the stress protocol: fear conditioning control (FCC, n=6), complex stress (ComS, n=9), and control (n=6). While the ComS experienced three types of stress (maternal separation, juvenile isolation, electric foot shock), the FCC only experienced an electric foot shock stress and the control never experienced any. We compared fear responses at postnatal day (PND) 29 and PND 56 through freezing time per episode (FTpE), total freezing time (TFT), total freezing episodes (TFE), and ultrasonic vocalization (USV). Results: ComS showed the longest FTpE in the conditioned fear response test. ComS and FCC exhibited the longer TFT and these two groups only displayed USV. ComS show difference TFE between PND 29 and PND 56. Conclusion: The results of this investigation show that complex stress may affect not quantity of fear response but characteristics of fear response. Longer FTpE may be associated with tonic immobility (TI) which could be considered as a failed self-protective reaction and might be analogous to a sign of inappropriate coping strategy and self-dysregulation in complex trauma patients.
Keywords: Complex trauma, Animal model, Anxiety, Freezing reaction, cataleptic, Ultrasonic vocalization


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