Axonal Transport of [ 3 H]Fucose‐Labeled Glycoproteins in Two Intra‐Brain Tracts of the Rat

[ 3 H]Fucose was stereotaxically injected into the dorsalateral geniculate body (DLGB) of adult male rats, and 1 h to 10 days post‐injection the DLGB and projection site (striate cortex) were dissected out and solubilized in 1% sodium dodecyl sulfate. Each sample was analyzed for acid‐precipitable radioactivity, and radioactivity in different molecular weight classes was determined following discontinuous gel electrophoresis in cylindrical gels. The specificity of transport of radioactive glycoprotein to the striate cortex was determined by autoradiography of brain sections. Acid‐precipitable radioactivity in the DLGB peaked at 5 to 6 h, plateaued, and then declined over the time course studied. The electrophoretic distribution pattern was complex, five bands containing fucosylated protein being initially prominent, as a percentage of radioactivity on the gel, and then decreasing with time. Two discrete waves of glycoproteins arriving at the visual cortex (between 3 and 4 h and between 12 and 48 h) were observed. Quantitative differences in distribution of molecular weight classes were noted between glycoproteins transported in these two waves. Of particular interest were rapidly turning‐over proteins of molecular weights of 110,000 and 120,000 (half‐time of less than 1 day). A study of the hippocampal commissural pathway, following introduction of radioactivity into one hippocampal formation, was also conducted. The electrophoretic distribution patterns of proteins, and the changes in distribution with time, were similar to the situation in the DLGB. However, in the contralateral hippocampus three discrete waves of transport were resolved (2 to 3 h, 4 to 5 h, and then a continued gradual increase followed by another prominent rise between 1 and 2 days). Relative turnover times of different protein peaks in the hippocampal and DLGB‐cortical system were also different.