The effects of environmental-nutritional interactions upon the development of the visual cortex were studied in Sprague-Dawley albino rats during lactation (5–22 postnatal days). Morphometric evaluations were assessed by measuring layer V pyramidal neurons, under camera lucida. The Golgi-Cox-Sholl technique permits quantitative studies of neurons by the precipitation of metallic mercury at random, without any selectivity. Length and frequency of dendritic segments showed significant differences due to rearing, nutrition, and topographic localization. Early environmental enrichment exerted its maximal benefits in undernourished pups, the influences being highly prominent in the lateroventral sector of the cortical plate that receives conspicuous inputs during development. These findings may provide bases for the design of clinical strategies to palliate the adverse effects of undernourishment and sensory deprivation on brain development, since their effects seem to follow pari passu the topographic sequences of cortical morphogenesis.

The effect of chronic yohimbine treatment early in life on packing density of neurons was evaluated in the occipital cortex of young rats. Yohimbine administration to pups between days 5 and 16 of postnatal life (2.5 mg/kg/day i.p.) resulted at 45 days of age in significantly higher neuronal density in layers II–V of the occipital cortex, the effect being more marked in the dorsal region than in the dorsolateral and lateral ones. Results suggest a relationship between enhanced central noradrenaline activity and altered development of the neuropil in the occipital cortex.