Age-related changes in the cerebellum: parallel fibers

Between the ages of 3 and 23 months, the cerebella of NIH Fischer 344 rats lose 30% of the thickness of the molecular layer, 60% of the length of parallel fibers, and 80% of the synaptic varicosities along parallel fibers. Nearly 60% of these synaptic varicosities disappear between 3 and 9 months. Thus, the loss of cerebellar synapses is unusual, may have begun early in life, and continue into old age, causing profound synaptic losses in older rats. In addition to serious implications to functional losses, we speculate that these synaptic losses may trigger other age-related cellular losses in the cerebellum.