Abstract: AIM: To investigate the effects of D-galactose on ultrastructure of rats'hypothalamic arcuate nucleus.Methods: 12 rats at age of 6 months were divided into two groups at random, the control and D-galactose group.Rats of control group were treated with saline solution by sc, and rats of D-galactose group were treated with D-galactose by sc at dose of 100 mg·kg^-1. Three months later the rats were killed by exsanguinating from heart.After being infused into the left ventricle with 2%-2.5% polyformaldehyde at the dose of 50 mg·kg^-1, the brains were taken and immerged in 2.5% polyformaldehyde, then the arcuate nucleus was taken according to the atlas of brain, the tissues taken were made into ultrathin sections to be observed under electron microscope.Results: comparing torats in control group, neurons of the arcuate nucleus of rats in D-galactose group appeared aging, the number of organelle in plasma decreased, but the number of lipochromesome in plasma increased significantly, and the size of neurons decreased also.Furthermore the apoptosis neuron was observed, the chromosome of which congregated around the nucleus'membrane, the typical aging neuron was also observed, the neuraxon of which was atrophying.But there were no obvious changes observed in neurons of the arcuate nucleus of rats in control group, plenty of organelles were observed under electron microscope clearly.Conclusion: Dgalactose can cause neurons of rats'arcuate nucleus aging, the neurons appeared atrophying and apoptosis.

Key words: D-galactose, arcuate nucleus, electron microscopic technique