Traumatic brain injury in late adolescent rats : effects on adulthood memory and anxiety

This article may not exactly replicate the final version published in the APA journal. It is not the copy of record.The consequences of traumatic brain injury (TBI) sustained during late adolescence (7 weeks-old) on spontaneous object recognition memory and on anxiety-like behaviors in the elevated plus maze were tested in rats during adulthood. Testing took place at two different post injury times, in separate groups: three and six weeks, when animals were 10 and 13 weeks old, respectively. The rats were either submitted to controlled cortical impact injury, an experimental model of focal TBI with contusion, or were shamoperated. TBI animals failed to remember the familiar object and had a significantly lower performance than sham-operated animals, indicating memory disruption, when the retention delay was 24 h, but not when it was 3 h. TBI did not have any significant effect on the main anxiety-related behaviors, but it reduced time in the central platform of the elevated plus maze. The effects of TBI on memory and on anxiety-like behaviors were similar at the two post injury times. In both TBI and sham-operated groups, animals tested six weeks after surgery had lower anxiety-related indices than those tested at three weeks, an effect that might be indicative of reduced anxiety levels with increasing age. In summary, focal TBI with contusion sustained during late adolescence led to object recognition memory deficits in a 24-h test during adulthood, but did not have a major impact on anxiety-like behaviors. Memory deficits persisted for at least six weeks after injury, indicating that spontaneous modifications of these functional disturbances did not take place along this time span