Citation

Sharma R, Sahota P, Thakkar MM. Sleep 2018; 41(3): e003.

Affiliation

Harry S. Truman Memorial Veterans Hospital and Department of Neurology, University of Missouri-School of Medicine, Columbia MO.

Copyright

(Copyright © 2018, American Academy of Sleep Medicine, Publisher Associated Professional Sleep Societies)

DOI

10.1093/sleep/zsy003

PMID

29346627

Abstract

Increasing evidences suggest that the predator threat model is a valid animal model of post-traumatic stress disorder (PTSD). However, sleep has never been examined in this model. Since sleep disturbances, including insomnia and excessive daytime sleepiness, are severe and protracted symptoms of PTSD, we hypothesized that mice exposed to predator odor trauma (POT) will display contextual fear conditioning along with severe and protracted sleep disruptions.Adult male C57BL/6J mice, instrumented with wire electrodes [to record hippocampal field potentials (LFP) and nuchal muscle (EMG) activity], were exposed to contextual conditioning using soiled cat litter as unconditional stimulus (US). On Day 1, fear memory acquisition training (FMA) was performed by exposing mice to contextual cage (conditional stimulus; CS) for 30 minutes followed by exposure to CS+US for 90 minutes. On Day 5, fear memory recall (FMR) testing was performed by exposing mice to CS (without US) for 120 minutes. LFP and EMG was recorded continuously for 5 days.Mice exposed to POT displayed 1) Hyperarousal coupled with electrophysiological indicators of memory acquisition and retrieval (increased hippocampal theta and gamma power) during FMA and FMR. 2) Increased NREM delta and REM theta power during sleep post-FMA, indicating memory consolidation. 3) Protracted sleep disturbances as evident by increased wakefulness; reduced NREM sleep and NREM delta power, increased NREM beta power during light (sleep) period. Increased sleep during dark (active) period.Based on these results, we suggest that mice exposed to POT display severe and protracted sleep disturbances mimicking sleep disturbance observed in human PTSD.

Published by Oxford University Press on behalf of Sleep Research Society (SRS) 2018. This work is written by (a) US Government employee(s) and is in the public domain in the US.

Language: en

Keywords

Predator odor trauma; contextual fear conditioning; gamma activity; hippocampal; insomnia; memory; sleep disturbances; theta