Age-related decrease in axonal transport measured by MR imaging in vivo
Section snippets
MnCl2 administration and MR scanning
Four male young (4 months) and three aged breeder (24–25 months, Charles River Labs) Sprague-Dawley rats had free access to food and water and were kept on a normal 12-h light/dark cycle. All procedures were approved by the University of Washington Animal Care Committee. The four young rats were scanned on 2 separate occasions at 4 months old and 13 to 17 months old (9 to 13 months apart) for a longitudinal assessment of decreased transport. In addition, to control for potential confounding
Statistical mapping indicates Mn2+ transport differences with age
Group-wise pixel-by-pixel statistical mapping indicated age-related decreases in manganese transport to the olfactory tract both anterior and posterior regions. Peak z-values for both anterior and posterior VOIs were calculated across time points from 1 h to 48 h. Using the threshold Z = 4.0 as indicating significantly increased enhancement, the young group showed significant manganese transport through the posterior tract as early as 11–12 h (Z = 6.0 and Z = 4.7, for anterior and posterior,
Discussion
The results of this study indicated age-associated axonal transport deficits including longitudinal differences in living rat brains. Longitudinal decrease in brain axonal transport rates of aged rats has not been reported previously. Investigations of axonal transport in the brain are limited, in part due to the relative inaccessibility of living brain neuronal tracts and the technical challenges inherent in studying a dynamic, sub-cellular process. Axonal transport rates have been shown to
Acknowledgments
This study is supported in part by Washington Alzheimer Disease Research Center Pilot Research grant, Washington National Primate Research Center grant NCRR P51 RR000166-41, and NINDS RO1 NS045254-01.
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