Shaking Up the Synapses: How Repeated Mild Traumatic Brain Injury Disrupts the fine balance of Synaptic Plasticity in the Juvenile Dentate Gyrus




Gross, Allyson

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In Canada, the occurrence of traumatic brain injury is on the rise, with over 165,000 people affected every year. This condition can arise from a variety of causes, including motor vehicle collisions, falls, sports-related incidents, or assaults. Adolescents are particularly susceptible to multiple head injuries due to increased participation in sports and high-risk activities. Repeated mild traumatic injury (r-mTBI) can exacerbate symptom severity and impede neuropsychological recovery, with cognitive and psychiatric changes such as memory impairment that may persist for months or even years. It is thought that the hippocampus, which is vulnerable to injury may be responsible for impairments in memory after r-mTBI. To investigate the influence of memory impairment following r-mTBI, we employed the awake closed head injury (ACHI) model, which entailed delivering eight impacts throughout the day to male juvenile rats (PND 25 – 29). Hippocampal slices were prepared one or seven days after the last injury for in vitro electrophysiological recordings, and we examined the potential for long-term potentiation (LTP) and two distinct long-term depression pathways in the medial perforant path (MPP) of the dentate gyrus (DG). These findings demonstrated that r-mTBI did not disrupt 1 Hz - LTD but did result in significant impairment in long-term potentiation (LTP) and 10 Hz - long-term depression (LTD) in the juvenile male dentate gyrus (DG). These data are the first to describe the adverse impact of r-mTBI on e-CB-dependent LTD in the male DG, which could help link a novel pathway impairment to the memory deficits observed in people who have suffered concussions.



traumatic brain injury, synaptic plasticity, long term potentiation, long term depression, mild traumatic brain injury, electrophysiology