Learning-induced changes in brain membrane cholesterol and fluidity: implications for brain aging

Studies were conducted to elucidate effects of learning on properties of brain membranes. Sprague-Dawley rats, (3-months-old) fed with normal Purina chow cakes, were trained in a T-maze. After reaching proper criteria, the animals were sacrificed, their brains dissected into hypothalamus, hippocampus, cortex and brainstem. The various brain regions were assayed for cholesterol, phospholipids and membrane lipid microviscosity. The salient findings were (a) a marked learning-induced decrease in the level of cholesterol in the hippocampal and cortical regions and (b) a learning-induced increase in the membrane lipid fluidity. We postulate that upon the learning impact, brain membranes undergo definite changes in the lipid membrane phase which participate in the transduction of the learning process into biochemical templates.