[Neurohistological study of the dendrites of lamina V-pyramidal neurons of the rat following recovery from postnatal malnutrition]

Abstract

By means of the GOLGI technique the influence of unspecific early postnatal undernourishment (from day 1 till day 20 of postnatal life followed by 40 days of recovery) on the spine morphology was investigated in the brain cortex of young adult animals, 60 days old. It was found that in experimental animals the three main spine types (thin spines, mushroom spines and stubby spines) had developed on apical lateral dendrites of cingulate pyramidal neurons, indicating the realization of the morphological characteristics of pyramidal neurons during starvation and recovery. However, in 60 days old control animals 65-70% of the spines belonged to the thin spine type, but in undernourished and rehabilitated animals the mushroom type is dominating and its percentage was found to have increased from 25-30% (controls) to 50% of all spines. Additionally, a significant enlargement of the stalked spines, especially of their synaptic end-knobs bearing spine heads was demonstrated in experimental animals. In undisturbed animals the short thin stem spine is considered to be necessary in a certain percentage to secure an optimum of resting activity in the neuron. The enhancement in the total spine number of 40-50% between day 20 (end of starvation) and day 60 (end of recovery), found earlier by us, taken together with the present results (increase in mushroom spines and spine head enlargement) point to a real new formation by division of previously enlarged mushroom spines as well as to transformations and shifts in the spine population during the recovery time. In the formation, development and maturation of the spines a change in their morphology from the filopodium-like type over the mushroom type and finally the thin stalked type may occur. Our results are discussed as being the expression of the neuronal plasticity persisting far into adulthood in order to enable the organism to react adaptive against changed living conditions.