TOPOGRAPHY AND CYTOARCHITECTURE OF THE AREA X OF THE SPINAL CORD IN POSTNATAL ONTOGENESIS OF THE RAT

Abstract

Objective - to study age-related changes in the topography and cytoarchitecture of the area X of the rat spinal cord at different stages of postnatal ontogenesis. Materials and methods. The study was carried out on pieces of the spinal cord taken at the level of the second thoracic segment of 65 female Wistar rats aged 3, 5, 7, 10, 15, 20, 30, 60, 90, 120, 150, 180, and 360 days (5 animals in each age group). The age-related changes in the square area of the lamina X, its neurons number per section, the density of neurons in the area of central canal and dorsal and ventral gray commisures were studied histologically on 14-mm-thick tangential cryosections stained by thionine according to Nissl method. Results. The area X on the transverse section of the spinal cord thoracic segment was clearly identified in 3-day-old rats. In the rat postnatal development, the area of the lamina X decreased, mainly due to the decrease in size of the dorsal gray commissure, despite the increase in the area of the ventral commissure, which was observed in rats older than 20 days. Simultaneously with a decrease in the area of lamina X, a decrease in the total number of its neurons per section was observed. The density of neurons around the circumference of the central canal decreased by the 7th day, in the dorsal gray commissure - by the 10th day, and in the region of the ventral grey commissure - by the 20th day. In rats older than 20 days, the density of neurons in the zone of the central canal and ventral gray commissure did not change, and in the dorsal gray commissure it increased again by 240 days, reaching the same indices as in 7-day-old rats. Conclusions. The area X and its individual regions, as well as the total number and the density of neurons per section, vary in different ways at different stages of postnatal ontogenesis. The data are of interest for the study of changes of the organization of gray matter of the spinal cord in the postnatal ontogenesis.

Keywords

area X / spinal cord / ontogenesis / rat

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Porseva V.V., Nozdrachev A.D.