Regional lipid composition in the rat brain.

The lipid composition of the brain is of great importance to its metabolism and function. Although much research has been done on regional brain lipid composition, studies usually suffer from limited brain regions or from limited lipids analyzed. We modified a previously described method for the separation of brain phospholipids and glycolipids, improving the separation and sensitivity of the method. Using this modified method, we measured the lipid composition of the frontal and entorhinal cortices, the hippocampus, basal ganglia, cerebellum, and medulla oblongata of five rats under nitrous oxide analgesia. Total lipid content was highest (p < 0.05) in the medulla oblongata (111.0 +/- 6.0 mg/g wet brain, X +/- SD) followed by the hippocampus (72.6 +/- 2.8), cerebellum (62.7 +/- 4.6), basal ganglia (62.6 +/- 1.5), frontal cortex (57.7 +/- 2.1), and entorhinal cortex (53.3 +/- 1.9). The areas with higher total lipid content (p < 0.05) also had higher percentages of cerebrosides (18.6 +/- 2.2 in the medulla oblongata vs 8.3 +/- 1.2 in the frontal cortex) and 40 to 50% lower levels of phosphatidylcholine and phosphatidylinositol. The relation between the ratio of cerebrosides plus sulfatides to phosphatidylcholine and the total lipid content indicates that differences in brain lipid composition between regions are attributable to their relative gray/white matter content.