Histochemical evidence for a catecholaminergic (presumably dopaminergic) projection from the ventral mesencephalic tegmentum to visual cortex in the cat.

An histochemical technique combining the retrograde transport of horseradish peroxidase (HRP) and catecholamine histofluorescence was used to identify those neurons of the cat's mesencephalic ventromedial tegmentum (VMT) which project to visual cortex. In a region corresponding to the ventral tegmental area-A10 nucleus we identified a group of fluorescent cells which were retrogradely labeled by HRP injections into visual cortex. It is suggested that these cells belong to a hitherto unknown, posterior part of the mesocortical dopaminergic system.