Immunocytochemical study of parvalbumin fibers and cell bodies in the rat hipothalamus

The distribution of parvalbumin (PA) cell bodies and fibers in the hypothalamus of the rat was studied using a monoclonal antibody and the avidin-biotin-peroxidase method. The densest clusters of immunoreactive perikarya were observed in the nuclei mamillare medialis, arcuatus and dorsomedialis hypothalami, whereas the corpus mamillare lateralis had the lowest density. The densest network of immunoreactive fibers was observed in the corpus mamillare lateralis and nucleus arcuatus. The corpus mamillare medialis contained a moderate number of PA fibers, whereas the nucleus dorsomedialis hypothalami had the lowest density of immunoreactive fibers. In addition, a large number of immunoreactive fibers was found in the tractus opticus and the tractus mamillo-thalamicus. Essentially, the distribution of PA in the rat hypothalamus after using a monoclonal antibody seems to be broader in comparison with previous studies carried out in the same diencephalic region of the rat. The presence of PA in several nuclei of the rat hypothalamus suggests that this protein could be directly or indirectly involved in neuroendocrine, limbic and visual functions.