[Quantitative studies of layer III pyramidal cells of the cingulate cortex of the rat]

The dendritic tree and the spine distribution at layer III pyramidal cells of the cingulate cortex in three months old male rats were evaluated quantitatively with Golgi-Kopsch impregnated brains. The analysed pyramidal cells were classified into three groups as to different lengths of their apical main dendrites. The spine values for a basal individual dendritic field show significant differences between these three groups. The layer III pyramidal neurons of the cingulate cortex exhibit on an average a total length of the dendrites of 2253 micron with a total 1507 visible spines. The total average of spines on the apical main dendrites amounts to 0,57 spines per micron, the average length of the apical main dendrites amounts to 217 micron. The apical values of spine densities are smaller than that of the basal values. The basal dendritic tree is more branched and exhibit a higher total length of the dendritic branches than that of the apical dendritic tree. The apical and basal differences as to spine densities and lengths of the dendritic branches results in an equality as to the total number of apical and basal spines per neuron. The values of the cingulate layer III pyramidal cells are smaller by comparison with those of the striate area. These results are closely related to the number of afferent terminations in both regions.