THE DENDRITIC TREES OF NEURONS FROM THE HIPPOCAMPAL-FORMATION OF PROTEIN-DEPRIVED ADULT-RATS - A QUANTITATIVE GOLGI-STUDY

We have recently shown that lengthy periods of low-protein feeding of the adult rat lead to deficits in the number of hippocampal granule an d pyramidal cells, and in the number of messy fiber synapses. These fi ndings prompted us to analyze the dendrites of these neurons to evalua te whether, under the same experimental conditions, degenerative and/o r plastic changes also take place at the dendritic level. The hippocam pal formations from five 8-month-old rats fed a low-protein diet (case in 8%) for 6 months from the age of 2 months and from five age-matched controls were Golgi-impregnated and the morphology of the dendritic t rees quantitatively studied. We found that in malnourished animals the re was a reduction in the number of dendritic branches in the dentate granule cells and in the apical dendritic arborizations of CA3 pyramid al neurons. In addition, in the dentate granule cells the spine densit y was markedly increased and the terminal dendritic segments were elon gated in malnourished animals. No alterations were found in the apical dendrites of CA1 pyramidal cells. The results obtained show that long periods of malnutrition induce marked, although not uniform, changes in the dendritic domain of the hippocampal neurons, which reflect the presence of both degenerating and regrowing mechanisms. These alterati ons are likely to affect the connectivity pattern of the hippocampal f ormation and, hence, the activity of the neuronal circuitries in which this region of the brain is involved.