[Quantitative studies on the dendritic spine distribution on the lamina-5 pyramidal cells in the anterior gyrus cinguli of the rat]

Abstract

At three months old male rats the spine-distribution of the main dendrite and of the apical and basal dendrites of 36 lamina V-pyramidal cells of the regio cingularis (anterior cingulate cortex) was analyzed (from every subregion -- neocortex, mesoneocortex, mesoarchicortex -- 12 neurons). 1. The limbic pyramidal neurons show the same spine-distribution at their main dendrite as neocortical neurons of other brain regions and other mammal-species do: after an initial segment with poor spines only there follows an rapid increase of the spine-values with an amount at a range of 150 mum from the perikaryon, thereafter spine-values decrease continuously and slowly up the branching into the terminal bundle. 2. Basal and apical lateral dendrites however show another spine-distribution: basally there is an increase of the spine-values from the 1st up to the 3rd order, followed by a decrease at subsequent orders. Apically spine-density decreases from the 1st up to the 4th order. 3. The spine-distribution at the parts of the dendritic tree is discussed as a general biological sign of pyramidal cells. 4. The total number of spines of lamina V-pyramidal cells in the regio cingularis (anterior cingulate cortex) is less than those in the sensomotoric cortex and in the hippocampus, which corresponds with the lower differentiation of the limbic cortex. 5. By means of a variance-analysis the pyramidal spine-values of the three subregions were compared: concerning the total number of spines of a pyramidal neuron there are significant differences between the three subregions; the values are in the ratio of 3 to 2 to 1 (Regio praecentralis agranularis, 2461; mesoneocortex, 1664; mesoarchicortex, 800). The significantly least spine-density of all parts of the dendritic tree you can find in lamina V-pyramidal cells of the mesoarchicortex. 6. The equality of the basal and apical spine-values in the mesoneocortex is due to less specialization of these neurons. 7. The spine-values for a single dendritic field (EDF) show the differences between the limbic subregions clearly: there are significant differences between the three subregions concerning not only the number of spines but also the spine-densities apically and basally.