Loss of neurons from the external cuneate nucleus of the ageing mouse brain.

The number of neurons in the ASH/TO mouse external cuneate nucleus was examined at 6, 15, 22, 25, 28 and 31 months of age. There is a highly significant decrease in the number of neurons between 6 and 31 months of age. Neuron loss begins at 15 months when degenerating neurons are first found in the nucleus and becomes more rapid with increasing age. It is suggested that neuronal loss is due to anterograde transneuronal degeneration following a loss of primary proprioceptive neurons, first from the spinal roots and later from the brainstem.