Dopaminergic innervation of the primary visual cortex in the rat, and some correlations with human cortex

Dopaminergic terminals have been identified in the primary visual cortex with three techniques; immunocytochemistry with an anti-dopamine antiserum, retrograde axonal transport techniques using unconjugated wheat germ agglutinin and HPLC determination of catecholamines and metabolites in microdissected sub-regions of occipital cortex in the rat. The results demonstrate a specific dopaminergic innervation, arising from the ventral tegmental area, which is found mainly in laminae VI and V, but with minor innervation also in lamina I. Dopaminergic innervation to adjacent cortical regions is also described. Neurochemical data from post-mortem human material suggests that a similar innervation exists in man. An analysis of the distribution of dopaminergic fibres in relation to the known connections and possible functions of the deep laminae of visual cortex suggests that dopaminergic axons may participate in the corticofugal control of visual afferent pathways.