TIME-SCALE AND EXTENT OF NEURONAL AND SYNAPTIC LOSS IN THE HIPPOCAMPAL-FORMATION OF MALNOURISHED ADULT-RATS

We have demonstrated that a prolonged low-protein diet induces neurona l and synaptic loss in the hippocampal formation of the adult rat. Bec ause 6 months of protein deprivation was the shortest period analyzed in the previous investigations, in the present study we have evaluated the length of the treatment period necessary to induce significant ch anges in the numbers of neurons and synapses. Groups of 2-month-old ra ts were analyzed: (1) and (2) malnourished for 1 and 3 months with a l ow-protein diet (8% casein); (3) and (4) age-matched control rats fed with a standard diet. Stereological methods were employed to estimate the total number of granule, hilar, CA3 and CA1 pyramidal cells and th e volume of the respective cell layers, the volume of the messy fiber system and the number and related quantitative features of messy fiber -CA3 synapses. No differences in the number of cells or synapses were found between I-month malnourished rats and the respective controls. H owever, in rats treated for 3 months the total number of granule cells , CA3 and CAI pyramidal cells was reduced, as was the total number of synapses. These findings indicate that the changes induced by protein deprivation progressively increase during the early phases of treatmen t and that they are already evident after 3 months of protein deprivat ion.