DOI: 10.5061/dryad.x0k6djhn4
title: Non-rapid eye movement sleep determines resilience to social stress

description: Resilience, the ability to overcome stressful conditions, is found in most
 mammals and varies significantly among individuals. A lack of resilience
 can lead to the development of neuropsychiatric and sleep disorders, often
 within the same individual. Despite extensive research into the brain
 mechanisms causing maladaptive behavioral-responses to stress, it is not
 clear why some individuals exhibit resilience.  To examine if
 sleep has a determinative role in maladaptive behavioral-response to
 social stress, we investigated individual variations in resilience using a
 social-defeat model for male mice. Our results reveal a direct, causal
 relationship between sleep amount and resilience—demonstrating that sleep
 increases after social-defeat stress only occur in resilient mice.
 Further, we found that within the prefrontal cortex, a regulator of
 maladaptive responses to stress, pre-existing differences in sleep
 regulation predict resilience. Overall, these results demonstrate that
 increased NREM sleep, mediated cortically, is an active response to
 social-defeat stress that is both necessary and sufficient for promoting
 resilience. They also show that differences in resilience are strongly
 correlated with inter-individual variability in sleep regulation.
description: Male, C57BL/6J mice (Jackson Laboratory, Bar Harbor, ME, USA;
 000664) were seven-weeks old at the start of all studies. CD-1 retired
 male breeders (Charles Rivers, age 3 to 6 months upon arrival) were used
 as aggressors. All mice were singly housed on shaved, pine bedding upon
 arrival, maintained on a 12:12 L:D lighting cycle for the remainder of the
 study and randomly assigned to treatment groups. Food and water were
 available ad libitum. All procedures involving animals received prior
 approval from the Morehouse School of Medicine Institutional Animal Care
 and Use Committee (approved protocol 21-02). <strong>Surgery: EEG and LFP
 electrodes.</strong>
 Electroencephalography (EEG): EEG and Electromyography (EMG)
 electrodes were implanted in isoflurane (1.5–3%) anesthetized mice.
 Carprofen was given post operatively for two days. A prefabricated head
 mount (Pinnacle Technology Inc., Lawrence, KS) was used to position three
 stainless-steel epidural screw electrodes. The first electrode
 (frontal—located over the frontal cortex) was placed 1.5 mm anterior to
 bregma and 1.5 mm lateral to the central suture, whereas the second two
 electrodes (interparietal—located over the visual cortex and common
 reference) were placed 2.5 mm posterior to bregma and 1.5 mm on either
 side of the central suture. The resulting two leads (frontal–interparietal
 and interparietal–interparietal) were referenced contralaterally. A fourth
 screw served as a ground. Electrical continuity between the screw
 electrode and head mount was aided by silver epoxy. EMG activity was
 monitored using stainless-steel Teflon-coated wires that were inserted
 bilaterally into the nuchal muscle.  The head mount (integrated 2 × 3 pin
 socket array) was secured to the skull with dental acrylic. Mice were
 allowed to recover for at least 14 days before sleep recording.