[Neuronal location of thalamic afferents in the cingulate area of the rat]

Lesions were placed in the rat anterior thalamus (nucleus mediodorsalis and nucleus anteromedialis) known to project to the cingulate cortex (area 24). Transneuronal degeneration signs were found at the apical and basal dendritic tree of lamina V- and lamina III-pyramidal neurons in Golgi-Kopsch preparations. The lesioned animals showed significant decreases in the dendritic spine-density of apical and basal single dendritic fields of lamina V- as well as lamina III-pyramids. The results suggest that in the area 24 of the rat the thalamic afferent fibres terminate at both these pyramidal neurons. The method used allowed no decision whether the thalamic afferents terminate directly at the pyramids or if interneurons are interconnected.