IMMUNOHISTOCHEMICAL STUDY OF CALBINDIN IN THE DEVELOPING CEREBELLUM OF THE RAT

Background. Calbindin is a calcium-binding protein that supports calcium homeostasis for the normal functioning of neurons. Purpose. To study the distribution of immunoreactivity of calbindin-D28K in the structures of the developing cerebellum of the rat.Material and methods. The study was performed on 16 outbred white rats of different age groups: 2-, 7-, 15-days (early postnatal period), 45-days (puberty period). The cerebellum samples were taken and fixed in zinc-ethanol-formaldehyde for immunohistochemistry. Calbindin-D28K immunoreactivity was determined on paraffin sections using primary polyclonal rabbit antibodies.Results. In the cerebellar cortex, calbindin immunoreactivity was detected on the 2nd day after development of Purkinje cells (PC) in their perikaryons, and by the 15th day in their dendrites and it did not change by the 45th day. In all terms of the study in PC, it was detected not only in the cytoplasm, but also in their nucleus. In the granular layer, calbindin immunoreactivity decreased in rats in postnatal ontogenesis, however, in adult rats, some neurons were moderately immunopositive. Among them, from the 15th day after birth, the calbindin-immunoreactive afferent nerve fibers running in the white matter were detected. There were no significant differences in the distribution of calbindin between the lobes of the cerebellum of different phylogenetic age. Conclusions. Considering that the expression of сalbindin-D28k is detected throughout the entire period of development of Purkinje cells, as well as its physiological role in maintaining the function and homeostasis of calcium in them, it can be concluded that сalbindin-D28k is a valuable marker for the morphofunctional characteristics of PC in the developing and adult cerebellum of rats in normal and pathological conditions.