VESICULAR FAST AXONAL-TRANSPORT RATES IN YOUNG AND OLD RAT AXONS

An isolated sciatic nerve preparation was used to measure the transpor t rates of more than 18,000 vesicles in 72 axons from young (3-4 month s of age) and old (24-26 months of age) rats from two strains (Harlan Sprague-Dawley and Fisher-344). Average anterograde and retrograde ves icle transport rates were significantly slower in the older animals. T he amount of slowing of anterograde vesicles was twice as great as the slowing of retrograde vesicles. Age-related slowing of vesicle transp ort was inversely proportional to vesicle speed, with the result that transport of the slowest and largest vesicles may essentially be block ed in older axons. One possible explanation for these data is that lon g-lived axonal cytoskeletal proteins are subject to age-related change s that impede vesicle transport.