Given that caffeine consumption is exponentially rising in adolescents and they are at increased risk for repetitive mild traumatic brain injury (RmTBI), we sought to examine the pathophysiological outcomes associated with early life caffeine consumption and RmTBI. Adolescent male and female Sprague Dawley rats received either caffeine in the drinking water or normal water and were then randomly assigned to 3 mild injuries using our lateral impact device or 3 sham procedures. Following injury induction, behavioral outcomes were measured with a test battery designed to examine symptoms consistent with clinical manifestation of PCS (balance and motor coordination, anxiety, short-term working memory, and depressive-like behaviours). In addition, pathophysiological outcomes were examined with histological measures of volume and cellular proliferation in the dentate gyrus, as well as microglia activation in the ventromedial hypothalamus. Finally, modifications to expression of 12 genes (Adora2a, App, Aqp4, Bdnf, Bmal1, Clock, Cry, Gfap, Orx1, Orx2, Per, Tau), in the prefrontal cortex, hippocampus, and/or the hypothalamus were assessed. We found that chronic caffeine consumption in adolescence altered normal developmental trajectories, as well as recovery from RmTBI. Of particular importance, many of the outcomes exhibited sex-dependent responses whereby the sex of the animal modified response to caffeine, RmTBI, and the combination of the two. These results suggest that caffeine consumption in adolescents at high risk for RmTBI should be monitored.

An old wives' tale, and strongly held dogma, maintains that one should be kept awake after a mild traumatic brain injury (mTBI) to prevent a coma. This, however, conflicts with the known benefits of sleep: repair and restoration. We therefore sought to examine the effects of sleep deprivation (SD) in the post-traumatic sleep period on post-concussion symptomology (PCS). Adolescent male and female rats were administered repetitive mTBIs (RmTBI) or sham injuries and were then assigned to 5 h of SD or left undisturbed. All animals were then tested using seven behavioral tasks validated to examine PCS, followed by analysis of serum cytokines, and quantitative real-time PCR for messenger RNA (mRNA) expression. Exposure to 3 SD epochs significantly impaired behavior in 4 of 7 of the measures, while RmTBI also produced dysfunction in 5 of 7 tests, but the effects of SD and RmTBI were not cumulative. SD induced long-lasting changes in serum levels of Tnf-α, IL6, and IL-1ß. mRNA expression in the pre-frontal cortex, hippocampus, hypothalamus, and anterior cingulate cortex was modified in response to SD and RmTBI; but similar to the behavioral measures, the mRNA changes were not cumulative. Consequently, we report that SD often produced impairments similar or worse than RmTBI, and sleep hygiene should become a priority for adolescent health.