Abstracts

#17 Behavioural and Immune Response after Repeated Pediatric Concussion


Allison Dyck, University of Manitoba; Tammy L. Ivanco, University of Manitoba


Introduction

Brain, behavior, and immune system activation are intertwined after brain injury. With an undeveloped sense of balance toddlers have a high risk for head injuries, and after a single concussion the risk of second injury increases substantially. Although many children appear well shortly after brain injury, there may be underlying neural mechanisms hard at work repairing the brain, potentially affecting normal development. We evaluated behavioural and biological outcomes of repeated pediatric concussion using a rodent model of concussion. We expected a dose-like effect, with the number of concussions associated with increasing brain inflammation and behavioural deficits.


Methods

Seventy-two rats were grouped by sex and injury status (0-3 hits) for a 2 x 4 design. The final injuries were conducted on post-natal day 24, similar developmentally to the human toddler. Rats completed three motor behaviour tasks the following day. Tissue was collected for analysis of glial fibrillary acidic protein (GFAP) expression, a marker of neuroinflammation.


Results

Separate MANOVAs were run on the behavioural and biological data. GFAP was highest after two concussions compared to the sham and, single or three concussion groups. An injury effect was revealed in the wire hanging task, rats’ stability progressively declined with each injury. The beam running task revealed an interaction of sex and injury status. The rotarod revealed a sex difference.


Conclusion

Concussion caused an increase in GFAP and a dose-like impact on behaviour deficits, supporting our hypothesis. The behavioural tasks indicated sex differences in the developing brain’s response to injury. Inflammation increases after concussion, and there may be a maximum response of GFAP after two successive injuries. Concussions cause cascades of responses in the brain. The recovery mechanisms are complicated by sex, age, and number of injuries. The highly variable outcome of concussion requires investigation tailored to several factors, particularly in children.