Fluid percussion brain injury in the developing and adult rat: a comparative study of mortality, morphology, intracranial pressure and mean arterial blood pressure.

Changes in intracranial pressure (ICP) and mean arterial blood pressure (MABP) were measured for 30 min following an experimental fluid percussion traumatic brain injury in postnatal day 17 (P17), P28 and adult rats. Under enflurane anesthesia the left femoral artery was cannulated for MABP measurements and a 20 gauge needle was stereotaxically positioned into the right lateral ventricle for ICP measurements. Three different injury severities (mild: 1.35-1.45 atm, moderate: 2.65-2.75 atm, severe: 3.65-3.75 atm) were delivered over the left parietal cortex to each of the age groups. The biomechanical/physiological results indicated that fluid percussion generated reproducible traumatic brain injuries in the developing rat. Furthermore, with increasing injury severity the physiological responses (in terms of ICP and MABP) became more pronounced, resulting in a corresponding increase in mortality (mild, moderate, severe, respectively, P17: 27%, 36%, 100%; P28: 33%, 30%, 75%; adult: 0%, 20%, 55%). Compared to adult animals, developing rats exhibited pronounced hypotension in response to closed head injury, which most likely explains the greater percent mortality among the younger animals. The utilization of this model will allow for future studies addressing the consequences of traumatic brain injury when it is sustained early in development.