Age related changes in neuron number in the combined ventral and lateral pontine nuclei of the mouse.

The ventral and lateral pontine nuclei of mice aged 6, 15, 22, 25, 28 and 31 months were examined in parasagittal 6 m sections using quantitative histological techniques. The total number of neurons in both nuclei declined from 13,983 +/- 326 at 6 months to 7,684 +/- 242 at 31 months. The decline in number began after 15 months at which age lipofuscin was first observed in the neuronal perikarya. The nuclear diameter of pontine neurons increased from 9.4 +/- 0.2 microns at 6 months to 10.9 +/- 0.1 microns at 31 months. The increase in nuclear diameter was first apparent at 25 months. The number of sections containing the nuclei did not change with age (mean 166 +/- 3).