A New Hypothesis about Neuronal Degeneration Appeared after a Rat Model of Menopause

Objective: Estrogen is suggested to be one of the most important regulators of neuronal function, including neuronal proliferation, survival and plasticity. There is a broad consensus that the loss of ovarian hormones is associated with neurodegeneration in the hippocampus that leads to cognitive impairment. Methods: A total of 8 female rats which were subjected to bilateral ovariectomy were included in this study. After ovariectomy, the rats were housed for 123 days in a standard laboratory. At the end of the 123 days, the rats were euthanized and the brain sections were investigated by conventional light microscopic and electron microscopic techniques. Results: The regular structure of almost all axon extensions was lost. The majority of these extensions had a sawtooth-like appearance in longitudinal section profiles. Especially in transfer section profiles of myelinated axons, some morphological changes were shown which may be matched up with light microscopic findings. Conclusions: Deficiency of estrogen will initially affect microtubule organization. When this organization breaks down, it will physically cause the distribution of the normal structure of axonal plasmalemma. This in turn will lead to the distribution of physical organizations of estrogen and other different types of receptors which are placed in both the membrane and microtubules in the axon. Copyright (C) 2011 S. Karger AG, Basel