Objective Sequelae of behavioral impairments associated with human traumatic brain injury (TBI) include neurobehavioral problems. We compared exploratory, cognitive, and depressive-like behaviors in pediatric and adult male mice exposed to controlled cortical impact (CCI). Methods Pediatric (21 to 25 days old) and adult (8 to 12 weeks old) male C57Bl/6 mice underwent CCI at a 2-mm depth of deflection. Hematoxylin and eosin staining was performed 3 to 7 days after recovery from CCI, and injury volume was analyzed using ImageJ. Neurobehavioral characterization after CCI was performed using the Barnes maze test (BMT), passive avoidance test, open-field test, light/dark test, tail suspension test, and rotarod test. Acutely and subacutely (3 and 7 days after CCI, respectively), CCI mice showed graded injury compared to sham mice for all analyzed deflection depths. Results Time-dependent differences in injury volume were noted between 3 and 7 days following 2-mm TBI in adult mice. In the BMT, 2-mm TBI adults showed spatial memory deficits compared to sham adults (P<0.05). However, no difference in spatial learning and memory was found between sham and 2-mm CCI groups among pediatric mice. The open-field test, light/dark test, and tail suspension test did not reveal differences in anxiety-like behaviors in both age groups. Conclusion Our findings revealed a graded injury response in both age groups. The BMT was an efficient cognitive test for assessing spatial/non-spatial learning following CCI in adult mice; however, spatial learning impairments in pediatric mice could not be assessed.

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Objective Hypoxic ischemia (HI) is a secondary insult that can cause fatal neurologic outcomes after traumatic brain injury (TBI), ranging from mild cognitive deficits to persistent vegetative states. We here aimed to unravel the underlying pathological mechanisms of HI injury in a TBI mouse model.Methods Neurobehavior, neuroinflammation, and oxidative stress were assessed in a mouse model of controlled cortical impact (CCI) injury followed by HI. Mice underwent CCI alone, CCI followed by HI, HI alone, or sham operation. HI was induced by one-vessel carotid ligation with 1 hour of 8% oxygen in nitrogen. Learning and memory were assessed using the novel object recognition test, contextual and cued fear conditioning, and Barnes maze test. Brain cytokine production and oxidative stress-related components were measured.Results Compared to TBI-only animals, TBI followed by HI mice exhibited significantly poorer survival and health scores, spatial learning and memory in the Barnes maze test, discrimination memory in the novel object recognition test, and fear memory following contextual and cued fear conditioning. Malondialdehyde levels were significantly lower, whereas glutathione peroxidase activity was significantly higher in TBI followed by HI mice compared to TBI-only and sham counterparts, respectively. Interleukin-6 levels were significantly higher in TBI followed by HI mice compared to both TBI-only and sham animals.Conclusion Post-traumatic HI aggravated deficits in spatial, fear, and discrimination memory in an experimental TBI mouse model. Our results suggest that increased neuroinflammation and oxidative stress contribute to HI-induced neurobehavioral impairments after TBI.