Free sterols of the rabbit optic nerve and cerebral white matter during ontogenic development.

Free sterol composition of the developing rabbit optic nerve was compared with that of the homologous cerebral white matter at corresponding stages of ontogeny. The sterols were detected and identified by means of combined gas-chromatography and mass spectrometry. The following free sterols were found in both the optic nerve and cerebral white matter: cholesterol, desmosterol, lanosterol, two dimethylsterols, which are probably 4,4-dimethyl-5 alpha-cholest-8,24-diene-3 beta-ol, with a molecular weight of 412, and 4 alpha, 14 alpha-dimethyl-5 alpha-cholest-7-ene-3 beta-ol, with a molecular weight of 414 and probably cholestene, with a molecular weight of 368. The sterol spectrum of the developing optic nerve differed not only from that of the mature nerve but also from that of age-matched white matter of the rabbit brain. The tri- and dimethyl-sterols, detected for the first time in the rabbit optic nerve and cerebral white matter, are natural components of the developing nervous tissue but they were not found in the mature nerve nor in cerebral white matter.