부산대학교 도서관

Stress can push individuals close to the threshold to depression. An individual's intrinsic vulnerability before a stressful event determines how close they come to the threshold of depression. Identification of vulnerability biomarkers at early (before the stressful event) and late (close to the threshold after the stressful event) stages would allow for corrective actions. Social defeat is a stressful event that triggers vulnerability to depression in half of exposed rats. We analyzed the sleep properties of rats before (baseline) and after (recovery) social defeat by telemetry electroencephalogram recordings. Using Gaussian partitioning, we identified three nonrapid eye movement stages (N-S1, N-S2, and N-S3) in rats based on a sleep depth index (relative 6 power) and a cortical activity index (fractal dimension). We found (1) that, at baseline, N-S3 lability and high-6 relative power in wake identified, with 82% accuracy, the population of rats that will become vulnerable to depression after social defeat, and (2) that, at recovery, N-S1 instability identified vulnerable rats with 83% accuracy. Thus, our study identified early and late sleep biomarkers of vulnerability to depression, opening the way to the development of treatments at a prodromal stage for high sensitivity to stress, and for stress-induced vulnerability to depression. Key words: sleep instability; social stress; NREM; resilience; BDNF; stress sensitization; microarousals Statement of Significance By an automatic algorithm based on a data-driven approach, we were able to automatically determine in rats the existence of three non-rapid eye movement subtypes presenting homologies with those observed in humans. This new method allowed us to follow the evolution of sleep anomalies up to vulnerability to depression. Deep sleep instability is the earliest sleep abnormality observed in vulnerable rats. A social defeat exposition that brings some animals close to the threshold for depression associates these sleep abnormalities with an instability of light sleep with onset of microarousals as well as a decrease of serum brain-derived neurotrophic factor. This original approach opens the door to the primary prevention of depression and provides answers on the genesis of vulnerability to depression.
Introduction Stress is a risk factor for depression. A characteristic feature of humans is the individual nature of the stress response. Even if two individuals experience the same stressor, they [...]