No neuron loss from hypothalamic nuclei of old male rats.

Neuron density, volume of the area and total neuron number were measured in the medial preoptic area, supraoptic nucleus, paraventricular nucleus, anterior hypothalamic area, ventromedial nucleus, dorsomedial nucleus and arcuate nucleus of the hypothalamus in young adult male rats (3.5-5 months old) and in old male rats (26-27 months old) of the Sprague-Dawley strain. There is no neuron loss in all measured areas. The results correlate well with the sex difference in the functional changes of the feedback response to sex steroids in old rats.