Undernutrition of rats during early life does not affect the total number of cortical neurons.

Undernutrition during early life is known to cause deficits and distortions in brain structure. However, it remains uncertain whether this includes a diminution of the total numbers of neurons. Recent advances in stereological techniques have made it possible to obtain unbiased estimates of total numbers of cells in well-defined biological structures. Rats were undernourished from day 16 of gestation to 30 postnatal days of age by standardized procedures. These rats and well-fed control rats were anaesthetized and killed by intracardiac perfusion with fixatives at 70 days of age. The left cerebral hemisphere from each animal was embedded in Paraplast and serially sectioned. The sections were analyzed via the Cavalieri principle to obtain the total cortical volume and by the "disector" method to estimate the numerical density of neurons in the cortex. These values were later used to compute estimates of the total number of cortical neurons for each animal. Well-fed control rats had 26.9 million cortical neurons, while the previously undernourished animals had 24.8 million. The difference between these two groups was not statistically significant. It therefore appears that undernutrition of rats during early postnatal life does not affect the total numbers of neurons in the cerebral cortex.