Time of the Day of Traumatic Brain Injury has Minimal Effects on Behavioral and Histological Outcomes in Mice of Both Sexes.

Abstract

Transcription of > 50% of the mammalian coding genes follows circadian rhythm in an organ-specific manner. Recent findings highlighted the influence of time of the day in the progression of various neurological diseases and therapies. In the present study, we evaluated the effect of time of occurrence of traumatic brain injury (TBI) on behavioral and neuropathological outcomes in mice of both sexes. Following a controlled cortical impact injury induced between Zeitgeber time (ZT)1-4 or ZT13-16, behavioral deficits and brain damage were evaluated. There were no significant differences in post-TBI motor function between groups ZT1-4 and ZT13-16 in either male or female mice compared with the sex-matched naïve control. TBI-induced anxiety-like behavior was significantly higher in the female ZT13-16 cohort compared to the naïve cohort; but, no difference was observed between injured groups in both sexes. Similarly, spatial learning and memory were not significantly different between the ZT1-4 and ZT13-16 groups in both sexes. Post-TBI cortical lesion volume was also not significantly different between ZT1-4 and ZT-13-16 groups in both sexes. The present study observed no significant effects of occurrence time on TBI-induced brain damage or behavioral deficits in male and female mice.