Effect of Experimental Litters Reduction during the Neonatal and Suckling? Periods of Ontogeny on Some Parameters of...

We compared the effect of litter reduction on day 1 (series I) and day 14 after birth (series II) on the weight of the brain and right hemisphere and on the morphometric indicators of the development of the anteroparietal lobe in rats. Animals from both experimental series showed signs of acceleration (higher body weight and weights of the testes and ovaries). In series I, the weight of the brain and hemisphere and the thickness of the cortex surpassed the control values; the numerical density of neurons in layers II and V was lower and the numerical density of gliocytes was higher than in the control. The size of the neuronal nuclei of these layers as well as the size of perikaryons of layer V neurons also surpassed the control. These differences can be considered as evidence of advanced brain development in experimental animals. In contrast, gravimetric and morphometric parameters in series II did not differ significantly from the control values. Thus, the factors that determine accelerated development of the brain after reduction of litter size in the neonatal period produced no similar effect after litter reduction on day 14 after birth.