[The influence of early postnatal undernourishment on the development of cortical neurons in the rat]

Abstract

The influence of early postnatal undernutrition on growth and maturation processes in pyramidal and stellate neurons of the cingulate cortex was investigated quantitatively in Golgi-Kopsch impregnated sections of the rat brain from 11, 20, 35 and 60 days old control and experimental animals. The starvation experiment was performed by separation the offspring from their mother for hours daily during the first three weeks of postnatal life, continued up to the 60th day by feeding only 5 g pellets per day (which a normal demand of about 20 to 25 gram a day). Data of dendritic ramification, length and spine density were collected as parameters for neuronal development and maturation. In undernourished animals a retardation of the neuron maturation was found. The inhibiting effect of starvation was most pronounced during those periods of brain development showing the highest intensity of the maturation processes in controls: these periods are for lamina V pyramids the early postnatal phase, for Lamina III pyramids the early and late postnatal phase, for interneurons the late postnatal phase only. Thus, the pattern of damage reflects the heterochronicity of maturation of different neuron types. The lamina V pyramids with relative rapid postnatal development were less affected, however, their main spine maturation period covering the 11th upto the 20th day in controls was found to be postponed and the spine density reached finally was diminished. The lamina III pyramids were stronger affected by starvation due to their immature state in the beginning of the experiment and their prolonged maturation. These cells showed remarkable deficits in the spine maturation along the apical side and basal dendrites during the first 3 weeks of postnatal life, in the apical main dendrite up to the 60th day. The most striking effect of starvation occurred in interneurons which differentiate postnatally late and slowly. In controls more than 50 per cent of the dendritic spines appear later than on postnatal day 20. In experimentals the spine density was reduced by 40% already on day 20. Moreover, the deficit increased on day 60 to reach a level of about 60%. These results give evidence for a longlasting injury of the neuropil as morphological basis for mental dysfunction.