Dependence of Some Indicators of Brain Development in 30-Day-Old Rats on the Dynamics of Body Weight Gain in the Neonatal and Suckling Periods in Litters of Different Sizes.

We analyzed the dependence of the weight of the brain, its hemispheres, and morphometric parameters of the parietal cortex and the hippocampus in 30-day-old Wistar rats on their body weight at the age of 1, 7, 14, 21, and 30 days. All the animals were from medium-sized litters. In 6 litters (experiment), 6 rat pups were left in each litter 1 day after delivery; in 6 other litters (control), their number remained unchanged (8-13 pups). In both groups, a positive correlation was revealed between the brain weight and body weight at the age of 1, 7, 14, 21, and 30 days. At the same time, the body weight in rats aged 7, 14, 21, and 30 days and the brain and hemisphere weight at the age of 30 days in the experimental group was significantly greater than in the control group. Rats of the experimental group had higher numerical density of gliocytes in layer II and V of the neocortex and a greater ratio of glia/neurons in these layers. The cortical neurons in the experimental rats were larger than in the control in field I of the hippocampus (p<0.05) and in layer II (p<0.05) and layer V (p>0.05) of the neocortex. The neuronal nuclei in rats from reduced litters were significantly larger than in control animals.