Neuroprotection, Photoperiod, and Sleep

After an acquired brain injury, responses that induce cell death are activated; however, neuroprotective mechanisms are also activated. The relation between these responses determines the destination of the damaged tissue. This relation presents variations throughout the day; numerous studies have shown that the onset of a stroke occurs preferably in the morning. In the rat, ischemia causes more damage when it is induced during the night. The damage caused by a traumatic brain injury (TBI), in the rat, varies depending on the time of day it is induced. Minor behavioral damage has been reported when the TBI occurs during the night, a period that coincides with the wakefulness of the rat. It also has been observed that sleep deprivation accelerates the recovery. Our group has documented that this is due, in part, to a difference in the degree of activation of cannabinergic, GABAergyc, and glutamatergic systems.