Brain lactate uptake increases at the site of impact after traumatic brain injury

Although glucose is the main carbohydrate energy substrate for the normal brain, several studies published over the last 10 years now challenge this assumption. The activated brain increases its metabolism to meet increased energy demands by glycolysis after injury. In vitro studies now show that lactate alone can serve as an energy source to maintain synaptic function. In this study, we used C-14-lactate to test the hypothesis that blood lactate is acutely taken up by the injured brain, after fluid percussion injury (FPI) in the rat. 50 mu Ci radioactive lactate was injected i.v. immediately after FPI, in injured and sham rats. After 30 min, the brain was removed, frozen, and cut into 20 mu m sections for autoradiography. Uptake of C-14-label was mainly concentrated at the injury site (2.5 times greater) although uninjured brain also took up the C-14-label. This increased concentration of radioactive lactate at the injury site suggests that the injured brain may use the lactate as an energy source. (C) 2000 Elsevier Science B.V. All rights reserved.