, Volume 28, Issue 3, pp 187-196

Dying-back of Purkinje cell dendrites with synapse loss in aging rats

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Qualitative and quantitative changes were found in the cerebellar circuitry of old as compared to young rats. The old group had a reduced number of synapses (at least 30%), however, there was an increase in the size of remaining synaptic components (13.5% for spine head volume, 66% for bouton volume, and 17% for the area of synaptic contact zones). Furthermore, there were pronounced morphological changes in the older group appearing as: 1) prominent lipofuscin bodies in Purkinje cell somata, 2) numerous myelinated fibers in the lower part of the molecular layer, 3) tortuous Purkinje cell dendrites in a thinned molecular layer, and 4) abundant vacuolar profiles and membrane swirls in small and intermediate-sized dendrites. Our findings suggest that Purkinje cell dendrites are dying-back reducing the target field for granule cells and that remaining synaptic sites compensate by increasing synaptic contact area as well as the size of pre- and postsynaptic structures.