Mild traumatic brain injury (mTBI) or concussion is a common injury worldwide leading to substantial medical costs and a high burden on society. In adolescents, falls and sports related trauma are often the causes of mTBI. Importantly, critical brain growth and development occurs during this sensitive period making the prospect of a brain injury a worrying phenomenon. Upwards of 70% of patients report circadian disruption following these injuries and this has been shown to impede recovery. Therefore, we sought to determine if core circadian clock gene expression was disrupted in rat model of repetitive mTBI (RmTBI). Male and female adolescent rats (n = 129) received sham or RmTBI. The animals were then euthanized at different times throughout the day and night. Tissue from the hypothalamus, cerebellum, hippocampus, liver, and small intestine were evaluated for the expression ofand. We found most clock genes varied across the day/night indicating circadian expression patterns. In the hypothalamus we found RmTBI altered the expression ofand bmal1 in addition to sex differences inand. In the cerebellum,,,,,andrhythms were all knocked out by RmTBI in addition to sex differences in,andexpression. We also detected a significant decrease in overall expression of all clock genes in males in the middle of the night. In the hippocampus we found that RmTBI changed the rhythm of rev-erb-α expression in addition to sex differences inexpression. In the liver we detected strong rhythms in all genes examined, however onlyexpression was knocked out by RmTBI, in addition we also detected sex differences inand. We also detected an overall decrease in female clock gene expression in the early night. In the small intestine, RmTBI alteredexpression and there were sex differences in. These results indicate that RmTBI alters core circadian clock gene expression in the central and peripheral nervous system in a time, tissue and sex dependent manner. This may be disrupting important phase relationships between the brain and peripheral nervous system and contributing to post-injury symptomology and also highlights the importance for time and sex dependent assessment of injury outcomes. per1, per2, cry1, clock, bmal1rev-erb-α cry1per2, cry1, clock, bmal1rev-erb- α per1per2cry1clock bmal1rev-erb-α cry1clock bmal1bmal1per2per2cry1cry1rev-erb-α
