Knockdown of ventral tegmental area mu-opioid receptors in rats prevents effects of social defeat stress: Implications for amphetamine cross-sensitization, social avoidance, weight regulation and expression of brain-derived neurotrophic factor

Early-life adverse experiences (first hit) lead to coping strategies that may confer resilience or vulnerability to later experienced stressful events (second hit) and the subsequent development of stress-related psychopathologies. Here, we investigated whether exposure to two stressors at different stages in life has long-term effects on emotional and cognitive capabilities, and whether the interaction between the two stressors influences stress resilience. Male rats were subjected to social defeat stress (SDS, first hit) in adolescence and to a single episode of prolonged stress (SPS, second hit) in adulthood. Behavioral outcomes, hippocampal expression of brain-derived neurotrophic factor, and plasma corticosterone levels were tested in adulthood. Rats exposed to both stressors exhibited resilience against the development of stress-induced alterations in emotional behaviors and spatial memory, but vulnerability to cued fear memory dysfunction. Rats subjected to both stressors demonstrated resilience against the SDS-induced alterations in hippocampal brain-derived neurotrophic factor expression and plasma corticosterone levels. SPS alone altered locomotion and spatial memory retention; these effects were absent in SDS-exposed rats later exposed to SPS. Our findings reveal that exposure to social stress during early adolescence influences the ability to cope with a second challenge experienced later in life.

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Upregulation of miR-195a inhibits brain-derived neurotrophic factor in mouse hippocampus and may contribute to depression-like behaviors induced by chronic social stress

Tropical Journal of Pharmaceutical Research ◽

10.4314/tjpr.v19i12.8 ◽

2021 ◽

Vol 19 (12) ◽

pp. 2537-2543

Author(s):

Xuping Wen ◽

Mingshuan Lin

Keyword(s):

Protein Expression ◽

Neurotrophic Factor ◽

Social Defeat ◽

Brain Derived Neurotrophic Factor ◽

Luciferase Reporter ◽

Control Group ◽

Social Defeat Stress ◽

Chronic Social Defeat Stress ◽

Mouse Hippocampus

Purpose: To explore the effect of miR-195a on nerve cells in the hippocampal region of depressionmodel mice.Methods: A chronic social defeat stress (CSDS) model was used as a depressed mouse model. In vivo, C57BL/6J mice received CSDS treatment or miR-195a antagomir. Depression-like behaviors were evaluated. In vitro, the target relationship between miR-195a and brain-derived neurotrophic factor (BDNF) was validated by luciferase reporter assays in HEK-293 cells. In primary cortical neurons, expression levels of miR-195a and BDNF mRNA were evaluated using quantitative polymerase chain reaction (qPCR). BDNF protein expression was determined by western blotting.Results: The sucrose preference ratio and social contact of the CSDS group were significantly decreased, whereas the immobility time was significantly increased, compared with the control group (p< 0.05). Interestingly, the expression of miR-195a was upregulated in the CSDS group compared with control group (p < 0.05). Bioinformatics prediction and luciferase reporter assay data indicate that miR195a bound the BDNF 3’ untranslated region. BDNF protein expression levels were significantly reduced by miR-195a mimic but increased by miR-195a inhibitor, compared with the negative control mimic group (p < 0.05). In vivo, miR-195a antagomir alleviated depression-like behaviors compared with CSDS group. In addition, miR-195a antagomir restored the expression of BDNF in mouse hippocampus in the CSDS group (p < 0.05).Conclusion: MiR-195a inhibitor ameliorates depression-like behaviors of depressed mice by downregulation of BDNF, whereas upregulation of miR-195a inhibits BDNF expression in mouse hippocampus and may contribute to depression. Keywords: Chronic social defeat stress, Depression, MiR-195, brain-derived neurotrophic factor, BDNF

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