A quantitative morphological study of some effects of undernutrition on rat body and brain growth
Rats undernourished during their suckling period have been shown to have significant deficits in the synapse-to-neuron ratios of certain brain regions. These deficits disappeared following a lengthy period of nutritional rehabilitation. It is possible that a longer period of undernutrition could cause larger or permanent deficits in this ratio. The present study was designed to test these hypotheses. Rat pups were undernourished from about birth until 100 days of-age by restriction of their food intake. Some rats were subsequently rehabilitated by feeding them ad libitum until 200 days. Six male rats in both control and experimental groups were killed by perfusion with gluteraldehyde at 12, 25, 50, 100 and 200 days-of-age. Body and various organ weights, as well as several skeletal dimensions and maturity were measured. Stereological procedures at the light and electron microscope level were used to estimate the synapse-to-neuron ratios in the visual cortices. The thickness of cortex in this brain region was also measured on coronal sections. The body and organs of experimental rats generally had persisting weight deficits compared with controls. Similar deficits were seen in most skeletal dimensions, with a delay in skeletal 'maturity' during the period of undernutrition. Cortical thickness was unaffected by undernutrition. However, there was a significant (P < 0.05) deficit in the synapse-to-neuron ratio of 100 day-old undernourished rats compared with controls. At 200 days the previously undernourished animals had significantly (P < 0.05) more synapses per neuron than controls. These results suggest that the lengthy period of undernutrition imposed in the present experiment had permanent effects on most body and organ weights as well as on skeletal dimensions. Skeletal maturity and synapse-to-neuron ratios were initially delayed but subsequently recovered.