Exposure to early life adversity alters the future behavioral response to a stressful challenge in BALB/C mice

Maternal separation regulates sensitivity of stress-induced depression in mice by affecting hippocampal metabolism

Depression is a serious mental illness. Previous studies found that early life stress (ELS) plays a vital role in the onset and progression of depression. However, relevant studies have not yet been able to explain the specific effects of early stress on stress-induced depression sensitivity and individual behavior during growth. Therefore, we constructed a maternal separation (MS) model and administered chronic social frustration stress at different stages of their growth while conducting metabolomics analysis on the hippocampus of mice. Our results showed that the immobility time of mice in the forced swimming test was significantly reduced at the end of MS. Meanwhile, mice with MS experience significantly decreased total movement distance in the open field test and sucrose preference ratio in the sucrose preference test when subjected to chronic social defeat stress (CSDS) during adolescence. In adulthood, the results were the opposite. In addition, we found that level changes in metabolites such as Beta-alanine, l-aspartic acid, 2-aminoadipic acid, and Glycine are closely related to behavioral changes. These metabolites are mainly enriched in Pantothenate, CoA biosynthesis, and Beta Alanine metabolism pathways. Our experiment revealed that the effects of ELS vary across different age groups. It will increase an individual's sensitivity to depression when facing CSDS in adolescence, but it will reduce their sensitivity to depression when facing CSDS in adulthood. This may be achieved by regulating the hippocampus's Pantothenate and CoA biosynthesis and Beta Alanine metabolism pathways represented by Beta-alanine, l-Aspartic acid, 2-aminoadipic acid, and Glycine metabolites.

Elevated fear responses to threatening cues in rats with early life stress is associated with greater excitability and loss of gamma oscillations in ventral-medial prefrontal cortex

Stress experienced early in development can have profound influences on developmental trajectories and ultimately behaviors in adulthood. Potent stressors during brain maturation can profoundly disrupt prefrontal cortical areas in particular, which can set the stage for prefrontal-dependent alterations in fear regulation and risk of drug abuse in adulthood. Despite these observations, few studies have investigated in vivo signaling in prefrontal signals in animals with a history of early life stress (ELS). Here, rats with ELS experienced during the first post-natal week were then tested on a conditioned suppression paradigm during adulthood. During conditioned suppression, electrophysiological recordings were made in the ventral medial prefrontal cortex (vmPFC) during presentations of a fear-associated cue that resolved both single-unit activity and local field potentials (LFPs). Relative to unstressed controls, ELS-experienced rats showed greater fear-related suppression of lever pressing. During presentations of the fear-associated cue (CS+), neurons in the vmPFC of ELS animals showed a significant increase in the probability of excitatory encoding relative to controls, and excitatory phasic responses in the ELS animals were reliably of higher magnitude than Controls. In contrast, vmPFC neurons in ELS subjects better discriminated between the shock-associated CS+ and the neutral ("safe") CS- cue than Controls. LFPs recorded in the same locations revealed that high gamma band (65-95 Hz) oscillations were strongly potentiated in Controls during presentation of the fear-associated CS+ cue, but this potentiation was abolished in ELS subjects. Notably, no other LFP spectra differed between ELS and Controls for either the CS+ or CS-. Collectively, these data suggest that ELS experience alters the neurobehavioral functions of PFC in adulthood that are critical for processing fear regulation. As such, these alterations may also provide insight into increased susceptibility to other PFC-dependent processes such as risk-based choice, motivation, and regulation of drug use and relapse in ELS populations.