Age related changes in neuron number in the mouse lateral vestibular nucleus.

The number of large neurons in the lateral vestibular nucleus of the mouse brain decreases in number after 25 months of age, from 488 at 25 months to 298 at 31 months. The number of small neurons in the nucleus remains constant up to 31 months of age. Large neurons accumulate lipofuscin from 25 months and their mean nuclear diameter increases significantly between 25 and 28 months of age. Small neurons contain very little lipofuscin even at 31 months of age and their mean nuclear diameter remains constant between 6 and 31 months. The difference in response of the two types of neurons to ageing may be due to their connections. Large neurons project to spinal motor neurons which decline in number with age and they receive projections from Purkinje cells in the anterior lobe of the cerebellum which also decline in number with age. Small neurons mainly project to the oculogyric nuclei in at least one of which (the abducens) there is no loss of neurons up to 31 months of age.