DIFFERENTIAL VULNERABILITY OF THE SUBICULUM AND ENTORHINAL CORTEX OF THE ADULT-RAT TO PROLONGED PROTEIN-DEPRIVATION

Protein deprivation experienced in adult life leads to deficits in the number of hippocampal granule and CA3-CA1 pyramidal cells and to chan ges in the dendritic domain of granule cells and CA3 pyramids. To obta in a more complete insight into the effects of malnutrition on the lim bic system of the adult rat we have analyzed the subiculum and the ent orhinal cortex (neuronal layers II, III, and V-VI) in groups of 8-mont h-old rats fed with a low-protein diet (8% casein) since the age of 2 months and in age-matched control rats. Stereological methods were emp loyed to estimate the total number of neurons in the subiculum and lay ers II, III, and V-VI of the entorhinal cortex and the volume of the r espective cell layers. Moreover, to evaluate whether protein deprivati on affects the dendritic domains of the neurons from these regions we have analyzed, in Golgi-impregnated material, the dendritic trees of t he pyramidal cells of the subiculum and of the stellate neurons of the entorhinal cortex layer II applying quantitative and metric methods. The volume of the subiculum and the total number of its neurons were r educed in malnourished animals. In these animals we also found marked regressive changes in the apical and basal dendritic trees of the pyra midal subicular neurons. However, the spine density was increased in m alnourished rats. No differences in the volume of the neuronal layers of the entorhinal cortex or in the total number of their neurons were found between protein-deprived and control rats, and no alterations we re depicted in the dendritic trees of the stellate neurons of layer II . We can thus conclude that the effects of long-term protein deprivati on are region specific and that the resulting structural alterations a re confined to the three-layered components of the hippocampal region. (C) 1998 Wiley-Liss, Inc.