Effect upon brain weight and cholesterol content of maintaining rats of various ages at constant weight.

Rats weighing 400 g were maintained at constant weight for 500 days. Their diet consisted of 14 g/day for the first 150 days and 13 g/day thereafter. A second group of rats weighing 350 g was fed 11.5 g/day for 400 days; at the end of the experiment, these rats weighed 382 g. Under these conditions, the increase in brain weight and in quantity and concentration of cholesterol in the brain as a function of time was identical to that observed in the control rats fed ad libitum. Rats weighting 250 g fed 8.5 g/day for 200 days showed a body weight increase of 16 g. Up to the age of 115 days, the evolution of brain weight in terms of time did not differ from that observed in control rats. Rats weighting 100 g and fed 4.5 g/day showed an increase of 28 g after 300 days. The increase in brain weight and in brain cholesterol content as a function of time was less than that observed in the control rats. A curve deduced from these results has the practical interest of indicating the daily energy requirement for maintaining rats at a chosen constant weight. Expressed in terms of body surface area, the daily energy intake appears constant. It was also observed that, when conditions of minimal economy are imposed upon the adult rat, brain nutrition is not modified. But for young rats (100 g),brain development under these nutrtional conditions is affected.