Behavioral Outcomes Differ between Rotational Acceleration and Blast Mechanisms of Mild Traumatic Brain Injury

Abstract

Mild traumatic brain injury (mTBI) can result from a number of mechanisms, including blunt impact, head rotational acceleration, exposure to blast, and penetration of projectiles. Mechanism is likely to influence the type, severity, and chronicity of outcomes. The objective of this study was to determine differences in the severity and time course of behavioral outcomes following blast and rotational mTBI. The Medical College of Wisconsin (MCW) Rotational Injury model and a shock tube model of primary blast injury were used to induce mTBI in rats and behavioral assessments were conducted within the first week, as well as 30 and 60 days following injury. Acute recovery time demonstrated similar increases over protocol-matched shams, indicating acute injury severity equivalence between the two mechanisms. Post-injury behavior in the elevated plus maze demonstrated differing trends, with rotationally injured rats acutely demonstrating greater activity, whereas blast-injured rats had decreased activity that developed at chronic time points. Similarly, blast-injured rats demonstrated trends associated with cognitive deficits that were not apparent following rotational injuries. These findings demonstrate that rotational and blast injury result in behavioral changes with different qualitative and temporal manifestations. Whereas rotational injury was characterized by a rapidly emerging phenotype consistent with behavioral disinhibition, blast injury was associated with emotional and cognitive differences that were not evident acutely, but developed later, with an anxiety-like phenotype still present in injured animals at our most chronic measurements.

Prediction of Post-Concussive Behavioral Changes in a Rodent Model Based on Head Rotational Acceleration Characteristics

“…Those changes resolved by more chronic post-injury time points. Contradictory findings between the current and prior studies incorporating different injury models is likely attributable to the mechanism of injury 41. Other studies using the rotational acceleration injury mechanism demonstrated similar EPM behaviors at acute time points.…”

“…Longer latencies following platform relocation would be indicative of an inability to adjust to the new platform location, an effect identified in other investigations involving sleep apnea and drug abuse 24,46. Additionally, although our group has not previously identified late-developing cognitive deficits following rotational acceleration injury, our prior blast TBI studies in rodents identified cognitive changes during chronic assessments that were either not present at the acute assessment41 or persisted and advanced from those identified at the acute assessment 6. These cognitive changes, identified in the current rodent model, may be associated with post-concussive syndrome in the human.…”

Repeated blast model of mild traumatic brain injury alters oxycodone self‐administration and drug seeking

“…(), Stemper et al . (). Briefly, rats were maintained under anesthesia with a continuous delivery of 1.5% isoflurane and administered Rimadyl (carprofen, 5 mg/kg, s.c. Zoetis Inc, Kalamazoo, MI, USA).…”

“…Rats were exposed to either repeated blast overpressure or repeated sham conditions as described previously in Budde et al (2013), Lim et al (2015), Stemper et al (2016). Briefly, rats were maintained under anesthesia with a continuous delivery of 1.5% isoflurane and administered Rimadyl (carprofen, 5 mg/kg, s.c. Zoetis Inc, Kalamazoo, MI, USA).…”

“…In this study, we investigated the effect of mTBI on various stages of oxycodone abuse. The model of mTBI used was a blast injury induced by exposing male Sprague Dawley rats to an overpressure wave produced using an experimental shock tube apparatus (Budde et al, 2013;Lim et al, 2015;Stemper et al, 2016). This blast TBI (bTBI) results in alterations in several brain regions, including the medial prefrontal cortex (mPFC) and insular cortex, that last at least 30 days post blast as observed by diffusion tensor imaging (Budde et al, 2013).…”