[Changes in the hypothalamic ultrastructure during aging].

Changes in the ultrastructure of neurons and synapses of the paraventricular nucleus of the hypothalamus were studied in old rats. The time-course of the pathomorphological alterations was shown. Dendrites, particularly those of medium size, were found to be especially vulnerable. The first signs of ultrastructural changes in neurons were shown in mitochondria. Although chromatolytic changes predominated in the majority of the hypothalamic neurons, hyperchronic alterations could also be observed. The nucleoli and nucleoliform formations in the cytoplasm proved the most "stable" components of neurons.