No abstract

Traumatic brain injury (TBI) is closely and bi-directionally linked with alcohol use, as by some estimates intoxication is the direct or indirect cause of one-third to one-half of all TBI cases. Alcohol use following injury can reduce the efficacy of rehabilitation and increase the chances for additional injury. Finally, TBI itself may be a risk factor for the development of alcohol use disorders. Children who suffer TBIs have poorer life outcomes and more risk of substance abuse. We used a standardized closed-head injury to model mild traumatic brain injuries. We found that mice injured as juveniles but not during adulthood exhibited much greater alcohol self-administration in adulthood. Further, this phenomenon was limited to female mice. Using behavioral testing, including conditioned place preference assays, we showed that early injuries increase the rewarding properties of alcohol. Environmental enrichment administered after injury reduced axonal degeneration and prevented the increase in drinking behavior. Additionally, brain-derived neurotrophic factor gene expression, which was reduced by TBI, was normalized by environmental enrichment. Together, these results suggest a novel model of alterations in reward circuitry following trauma during development.

Traumatic brain injury (TBI)-induced impairments in cerebral energy metabolism impede tissue repair and contribute to delayed functional recovery. Moreover, the transient alteration in brain glucose utilization corresponds to a period of increased vulnerability to the negative effects of a subsequent TBI. In order to better understand the factors contributing to TBI-induced central metabolic dysfunction, we examined the effect of single and repeated TBIs on brain insulin signalling. Here we show that TBI induced acute brain insulin resistance, which resolved within 7 days following a single injury but persisted until 28 days following repeated injuries. Obesity, which causes brain insulin resistance and neuroinflammation, exacerbated the consequences of TBI. Obese mice that underwent a TBI exhibited a prolonged reduction of Akt (also known as protein kinase B) signalling, exacerbated neuroinflammation (microglial activation), learning and memory deficits, and anxiety-like behaviours. Taken together, the transient changes in brain insulin sensitivity following TBI suggest a reduced capacity of the injured brain to respond to the neuroprotective and anti-inflammatory actions of insulin and Akt signalling, and thus may be a contributing factor for the damaging neuroinflammation and long-lasting deficits that occur following TBI.

No abstract

No abstract