Abstract
C57BL/6NKorl mice are a novel mouse stock recently developed by the National Institute of Food and Drug Safety Evaluation in Korea. Extensive research into the nature of C57BL/6NKorl mice is being conducted. However, there is no scientific evidence for the phenotypic response to restraint stress (RST), a stress paradigm for modeling depressive disorders, in rodents. In this study, we investigated the repeated RST-induced depressive-like phenotypes in C57BL/6 N mouse substrains (viz., C57BL/6NKorl mice from Korea, C57BL/6NA mice from the United States, and C57BL/6NB mice from Japan) obtained from different sources. The results showed that C57BL/6 N mice derived from various sources exposed to repeated RST resulted in depressive-like phenotypes reflected by a similar degree of behavioral modification and susceptibility to oxidative stress in a duration-dependent manner, except for the distinctive features (increased body weight (BW) and tolerance to the suppression of BW gain by exposure to repeated RST) in C57BL/6NKorl mice. Taken together, the duration-dependent alteration in depressive-like phenotypes by repeated exposure to RST observed in this study may provide valuable insights into the nature of C57BL/6NKorl mice as an alternative animal resource for better understanding of the etiology of depressive disorders and the mechanisms of antidepressant actions.
Highlights
Depression is a mental disorder characterized by psychological symptoms such as continuous low mood or sadness, diminished interest or pleasure in activities, anxiety, and social life disability
C57BL/6NA and C57BL/6NB mice showed a duration-dependent suppression in body weight (BW) gain following exposure to repeated restraint stress (RST), whereas C57BL/6NKorl mice were found to have the lowest BW in mice exposed to RST for 7 days, indicating a tolerance to stress-induced suppression of BW gain after 14 days of RST treatment (Fig. 1)
These results suggest that C57BL/6NKorl mice possess a distinctive feature regarding BW changes with relatively higher BW and adaptive response to exposure to repeated RST
Summary
Depression is a mental disorder characterized by psychological symptoms such as continuous low mood or sadness, diminished interest or pleasure in activities, anxiety, and social life disability. The prevalence of depression and depressive-like symptoms has been increasing in recent decades [1, 2]. Various causative risk factors have been reported to increase the risk of depressive disorder, but its pathophysiology is not fully understood. To better understand the etiology of it has been reported that chronic stress can precipitate a psychiatric disorder with increased susceptibility to developing anxiety- and depressive-like phenotypes [3]. Exposure to chronic stress is associated with an imbalance in neurotransmitters and negative feedback on the activation of the hypothalamic-pituitaryadrenal axis, which in turn induces adrenal secretion of glucocorticoids, corticosterone (CORT) in rodents, and cortisol in humans [5, 6].
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