Cellular Growth in Various Regions of the Developing Rat Brain

Abstract

Extract: The cellular growth patterns in whole brain, cerebrum, cerebellum, hippocampus, and brainstem were examined in rats between 6 and 22 days of age. When weight alone was measured, little difference was seen between the various regions; however, when cell number (DNA) or protein per cell (protein: DNA) was measured, regional differences became very striking.In the cerebellum, DNA content increased 8.5 fold between 6 and 17 days and subsequently tapered off. The protein: DNA ratio declined during this period. Although the increase in cell number in the cerebrum was only 2.5 fold, it continued until 21 days, at which time the experiment was terminated. After 10 days there was also an increase in the protein: DNA ratio. In the brainstem, there was a modest increase in cell number between 6 and 14 days. After 10 days the protein: DNA ratio increased 4 fold. In the hippocampus, there was a discrete increase in cell number only between 14 and 17 days.These data demonstrate the existence of distinct regional patterns of cellular growth during postnatal maturation of rat brain.Speculation: The brain, although often viewed as a discrete organ, is composed of a number of anatomically distinct regions that perform separate and unique functions. Previous data from this laboratory have shown that cell division ceases in whole rat brain by 21 days postnatally and in whole human brain by six months of age. This study demonstrates that various regions of rat brain have different rates of cell division and that the entire pattern of cellular growth is regionally specific. Since certain functions are regionally controlled, it is possible that the regional growth patterns described here have functional correlates.Alteration in the environment (nutrition) is known to affect the rate of cell division in whole brain. It is possible that environmental effects may be regionally specific. By studying the effects of environmental stimuli (anoxia or malnutrition) on regional growth patterns and correlating these effects with functional changes, it may be possible to relate cellular changes to functional deficits.