Figure 3. At high doses, caffeine increases energy metabolism at all brain levels. These color-coded autoradiographic images show the effect of caffeine on the rates of cerebral glucose utilization in rat brain sections taken at the level of the nucleus accumbens and caudate and raphe nuclei as shown by the arrows and the black areas in the anatomical reference sections (left). The color scale (right) represents quantitative rates of glucose utilization (in µmol/100 g/min). Acute injection of 1 mg caffeine/kg body wt induced an increase in LCMR_glc in the caudate and raphe nuclei but no change in the nucleus accumbens. Conversely, 10 mg caffeine/kg body wt induced a generalized increase in the rates of energy metabolism at all brain levels.