Morphometric and Immunocytochemical Analysis of Age-Related Changes in Neuropeptidergic Neurons

A variety of methodologies, including fetal transplantation, electrophysiology, and molecular biological techniques, are now available to the neuroscientist interested in determining how the central nervous system and neuroendocrine systems change with age. The aim of our studies has been to examine the morphology, biochemistry, and physiology of neurons that are important to the modulation of gonadotropin hormone-releasing hormone (GnRH). This review focuses on neuroanatomical analyses. The nature of morphological changes in the CNS that result in the loss of normal reproductive cyclicity with aging have been unknown until now. Our studies have attempted to examine cytoarchitectural relationships between peptidergic and GnRH neurons in the rostral forebrain and the hypothalamus in order to determine the mechanism for the loss of reproductive capacity in the aging female C57BL/6J mouse. We have employed light and electron microscopic, morphometric, and immunocytochemical techniques. Our studies have shown that only specific subregions, and specific neurons within these regions, are susceptible to age-related changes. Removal of the ovary over the long term has failed to protect against any observed neuroanatomical alteration. Our neuroanatomical data clearly suggest that functional changes in neuroendocrine systems occur both with and without concomitant death of neurons.