Distribution of cholesterol and galactosylceramide in rat cerebellar white matter

White matter and the inner granular layer of rat cerebellum was analysed by imaging time-of-flight secondary-ion mass spectrometry (TOF-SIMS) equipped with a Bi+ ion cluster gun. Samples were prepared by high pressure freezing, freeze-fracturing and freeze drying or by plunge freezing and cryostat sectioning. The identified and localized chemical species were: sodium, potassium, phosphocholine, cholesterol and galactosylceramide (Ga1C) with carbon chain lengths C18:0 (N-stearoyl-galactosylcerai-nide) and C24:0 (N-lignoceroylgalactosylceramide) with CH24:0 (hydroxy-lignoceroylgalactosylceramide). We report new findings regarding the organization of myelin in white matter. One is cholesterol-rich, ribbon-shaped 10-20 mu m areas excluding Na+ and K+. The second finding is the different distribution of Ga1C C18 and Ga1C C24 in relation to these areas, where Ga1C C18 was localized in cholesterol-rich areas and Ga1C C24 was localized in Na/K-enriched areas. The distribution of Ga1C was in small spots, homogeneous in size, of 0.8-1.5 mu m. Sample preparation with high pressure freezing allowed separate localization of sodium and potassium in tissue samples. (c) 2006 Elsevier B.V. All rights reserved.