Severity of experimental brain injury on lactate and free fatty acid accumulation and Evans blue extravasation in the rat cortex and hippocampus

Lactate and free fatty acids (FFAs) were extracted from the cortices and hi ppocampi of rats subjected to sham operation, or mild (1.25 atm) or moderat e (2.0 atm) fluid percussion (FP) injury, and their total tissue concentrat ions were measured. The elevation of lactate in the injured left cortex (IC ) and ipsilateral hippocampus (IH) was significantly greater in the moderat e-injury than in the mild-injury group at most test times between 5 min and 48 h after injury. Levels of total FFAs were elevated in the IC and IH to a greater extent and for a longer period after injury in the moderate-injur y (up to 48 h) than in the mild-injury group (up to 20 min), In general, th e extent and duration of the elevation of most of the individual FFAs (palm itic, stearic, oleic, and arachidonic acids) in the IC and IH were also gre ater in the moderate-injury group than in the mild-injury group. In the con tralateral cortex (CC) and hippocampus (CH), the elevation of lactate and t otal FFAs (and individual stearic and arachidonic acids) were also greater in the moderate-injury group than in the low-injury group at 5 min after in jury, The extravasation of Evans blue in the IC and IH from 3 to 6 h after injury was also the greatest in the moderate injury group. The hippocampal CA3 neuronal cell loss, but not cortical lesion volume, also increased with the severity of injury. These findings suggest that certain neurochemical, physiological (blood-brain barrier permeability), and morphologic response s increase with the severity of FP brain injury, and such relationships are consistent with the increased behavioral deficits observed with the increa se of severity of brain injury.