(1) PURPOSE- TBI in Veterans can often be a chronic condition and produce long-term sleep and behavioral problems. Insomnia in the context of TBI is reported in 30–60% of individuals following TBI and produces significant morbidity, daytime cognitive problems and impedes the quality of life. This proposal examines the impact of sleep aberrations and cognitive and behavioral disturbances in a mouse model of chronic TBI (CCI). Neural ORX dysregulation appears to be a mechanism for sleep and behavioral disturbances and provides an opportunity to treat with orexinergic agents. We propose to examine the effects of a dual orexin receptor antagonist treatment (DORA) on sleep, cognition, anxiety, and fearfulness in a mouse model of TBI. (2) BACKGROUND- (a) Scientific Rationale- ORX activates neural circuits by regulating awake state and arousal, anxiety, cognition, and other behaviors through widespread neural projections. Because ORX system abnormalities in the LH develop after TBI, ORX sleep-wake disruptions are hypothesized to contribute to chronic sleep and behavioral disturbances. Lemborexant (LEM) is a commercially available DORA that blocks orexin OX1 and OX2 receptors and improves sleep latency and maintenance in primary insomnia in both humans and animal models. LEM treatment is hypothesized to reverse sleep abnormalities and improve cognition and daytime behaviors produced by TBI. (b) How This Research Will Advance Biomedical Knowledge- (c) Significance of the Research and How it Relates to Priority Areas – This grant represents a potential high- impact translational proposal for a mechanism-based treatment for insomnia and other behavioral disturbances in chronic TBI. This proposal by experienced investigators (Kaplan and Zielinski) seeks to explore new research in areas where they have not previously been funded. As such, it responds to RX-20-009 as a TBI Small Project in Rehabilitation Research (SPiRE). (d) Direct Benefits and Quality of Services- If the utility of LEM on sleep disturbances, anxiety, and cognition can be demonstrated in proposed SPiRE studies, then larger scale studies using commercially available DORAs in animals and then Veterans with TBI can be pursued. (3) EXPECTED OUTCOMES OR PRODUCTS– Chronic CCI is anticipated to produce sleep abnormalities including: increased sleep latency and wake bouts, reduced total sleep time and sleeping bouts, disturbances of REM and NREM sleep, and sleep fragmentation. LEM is hypothesized to reverse these sleep abnormalities compared to vehicle treatment. CCI is expected to produce impaired memory in NOR test, greater anxiety as measured by decreased exploration in LDTT task and increase aberrant FR after FC. It is expected that LEM reverses these behavioral impairments in the CCI group. CCI is expected to produce reductions of ORX-A and -B levels in LH that are inversely correlated with sleep and behavioral disturbances. (4) METHODS AND RESEARCH PLAN- We examine a model of CCI vs. sham CCI in male and female C57BL/6 mice. In Aim 1, we examine the effects of single- and repeated-dose effects LEM (0, 10, 30, mg/kg) in CCI and sham CCI, at two months post-injury, on sleep parameters via sleep qEEG (measures of sleep latency, wake time, total sleep, NREM and REM sleep and delta EEG sleep). In Aim 2, we propose to measure the effects of single- and repeated-dose effects LEM in CCI on cognition using the NOR task. We examine LEM effects in the LDTT to measure motor behavior and anxiety in exploring a novel environment. Finally, we measure LEM effects in a fear conditioning test and measure LEM effects on with cue-induced FR. In Aims 1 and 2, we measure ORX-A and -B levels in LH using IHC and examine relationships between ORX-A and ORX-B neuropeptide expression and behaviors.

TBI is often a chronic disorder afflicting many Veterans and is associated with sleep-wake abnormalities and daytime cognitive and behavioral problems. Humans with TBI and rodent models of TBI demonstrate many sleep problems including problems in falling asleep, frequent awakenings, less total sleep, and resultant daytime problems with memory loss and anxiety. We have developed a mouse model of chronic TBI that identifies sleep-wake disturbances by electroencephalogram (EEG). One brain mechanism for these sleep- wake problems in TBI involves the neuropeptide orexin (ORX). We propose to test the treatment effects of an ORX receptor antagonist medication in male and female mice with chronic TBI. This medication, lemborexant, may reverse sleep EEG changes and restore sleep and behavioral functions. Relevance to Veterans Health: Many Veterans with chronic TBI have sleep problems, greater morbidity and poorer quality of life. This pilot proposal can ultimately lead ultimately to trials of these commercially available treatments in Veterans.