Alterations in regional brain catecholamine concentrations after experimental brain injury in the rat

Although activation of brain catecholaminergic systems has been implicated in the cerebrovascular and metabolic changes during subarachnoid hemorrhage, cerebral ischemia, cortical ablation, and cortical freeze lesions, little is known of the response of regional brain catecholamine systems to traumatic brain injury. The present study was designed to characterize the temporal changes in concentrations of norepinephrine (NE), dopamine (DA), and epinephrine (E) in discrete brain regions following experimental fluid-percussion traumatic brain injury in rats. Anesthetized rats were subjected to fluid-percussion brain injury of moderate severity (2.2-2.3 atm) and killed at 1 h, 6 h, 24 h, 1 week, and 2 weeks postinjury (n = 6 per timepoint). Control animals (surgery and anesthesia without injury) were killed at identical timepoints (n = 6 per timepoint). Tissue concentrations of NE, DA, and E were evaluated using HPLC. Following brain injury, an acute decrease was observed in DA concentrations in the injured cortex (p < 0.05) at 1 h postinjury, which persisted up to 2 weeks postinjury. Striatal concentrations of DA were significantly increased (p < 0.05) only at 6 h postinjury. Hypothalamic concentrations of DA and NE increased significantly beginning at 1 h postinjury (p < 0.05 and p < 0.05, respectively) and persisted up to 24 h for DA (p < 0.05) and 1 week (p < 0.05) for NE. These data suggest that acute alterations occur in regional concentrations of brain catecholamines following brain trauma, which may persist for prolonged periods postinjury.