Origin of dopaminergic innervation of the rat hippocampal formation.

The origin of the dopaminergic afferents to the rat hippocampal formation has been investigated by measuring dopamine and DOPAC contents in this area after electrolytic or chemical lesion of the ventral tegmental area (A10) or substantia nigra (A9). The present study indicates that dopaminergic afferents to the hippocampal formation originate from the A10 and A9 dopaminergic cell groups. The 'anterior' hippocampal formation receives a major input from the A10 area whereas the 'posterior' hippocampal region receives dopaminergic afferents from both A9 and A10 cell groups. The dopaminergic afferents are entering the hippocampal region mainly through the dorsal route.