Influence of Litter Reduction in the Neonatal Period at Different Times after Birth on the Parameters of Brain Development in Rats.

We studied the brain of 5- and 14-day-old intact (control group) rats and rats of the same age from litters experimentally reduced on days 1 and 5 after birth (experimental groups). In animals of both experimental subgroups, the brain had morphological signs of advanced development: greater weight of the brain and hemisphere, greater thickness of the cortex, its molecular layer, lower numerical density of neurons in the anterior parietal and proper parietal lobes, greater sizes of neurons, their nuclei, and nucleoli in the neocortex of these zones, and increased concentration of RNA in the cytoplasm of neurons. These data suggest that the rate of brain development in rats can be accelerated under the influence of environmental changes that occur after litter reduction during the neonatal period at different times after birth.