Chronic stress and stressful emotional contagion affect the empathy-like behavior of rats

Contagion of depression: a double-edged sword

Depression is a significant mental health issue with extensive economic implications, and recent studies suggest it may be transmitted between individuals. However, the mechanisms of this contagion remain unclear, and the social buffering effect has been understudied. This research employs three rodent models, including stress crossover, cohabitation-induced, and non-contact induced depression contagion models, to explore these mechanisms. Here, we report that that naive mice cohabiting with depressed mice showed increased corticosterone levels and depressive behaviors, unlike those with stressed mice, who did not exhibit these changes and even mitigated desperation in stressed mice. Non-contact cohabitation did not produce significant behavioral differences, but exposure to bedding from depressed mice reduced sucrose preference in naive mice. This study introduces reliable models of depression contagion, suggesting it operates independently of stress transmission. The interplay between depression contagion and social buffering may vary in different contexts. These findings provide new insights into the mechanisms of depression contagion and potential strategies for preventing depressive disorders.

Traditional Pediatric Massage Enhanced Hippocampal GR, BDNF and IGF-1 Expressions and Exerted an Anti-depressant Effect in an Adolescent Rat Model of CUMS-induced Depression

This study aimed to investigate the anti-depressant effect of traditional pediatric massage (TPM) in adolescent rats and its possible mechanism. The adolescent depression model in rats was established by using chronic unpredictable mild stress (CUMS). All rats were randomly divided into five groups (seven per group), including the groups of control (CON), CUMS, CUMS with TPM, CUMS with back stroking massage (BSM) and CUMS with fluoxetine (FLX). The tests of sucrose preference, Morris water maze and elevated plus maze were used to evaluate depression-related behaviors. Plasma corticosterone (CORT) level was measured by ELISA. The gene and protein expressions of glucocorticoid receptor (GR), brain-derived neurotrophic factor (BDNF) and insulin-like growth factor-1 (IGF-1) were measured by RT-qPCR and IHC respectively. The results showed that CUMS induced depression-related behaviors in the adolescent rats, along with decreased weight gain and reduced hippocampal expressions of GR, IGF-1 and BDNF. TPM could effectively prevent depression-related behaviors in CUMS-exposed adolescent rats, manifested as increasing weight gain, sucrose consumption, ratio of open-arm entry, times of crossing the specific quadrant and shortening escape latency. TPM also decreased CORT level in plasma, together with enhancing expressions of GR, IGF-1 and BDNF in the hippocampus. These results may support the clinical application of TPM to prevent and treat adolescent depression.