Changes in the Immunohistochemical Characteristics of Neurons in a Number of Hypothalamic Nuclei on Aging

Objectives. To identify changes in the immunohistochemical characteristics of neurons in the arcuate (AN), ventromedial (VMN), and dorsomedial (DMN) nuclei of the hypothalamus in rats on aging. Materials and methods. Studies were performed using male Wistar rats aged 3–4 months (five individuals) and 12–18 months (five individuals) using immunohistochemical methods. Results. Aging was associated with a decrease in the relative content of calbindin-immunopositive neurons in the DMN, while calretinin-immunopositive neurons in the DMN and VMN increased. The numbers of neurons immunopositive for neuronal nitric oxide synthase and the level of immunofluorescence for this enzyme were greater in all the nuclei studied in older animals. Older rats also showed a higher density of neuropeptide Y-immunopositive fibers in the VMN, with a smaller number in the DMN. Conclusions. Aging was associated with changes in the neurochemical composition of neurons, mainly in the ventromedial and dorsomedial nuclei of the hypothalamus.