The organization of dopaminergic and non-dopaminergic mesencephalo-cortical neurons in the rat

The dopamine containing mesencephalo-cortical pathway was studied in the rat by means of a combined retrograde fluorescent tracing and catecholamine histofluorescence technique. After large injections of the fluorescent retrograde tracer, Evans blue, into the frontal cortex, many neural somata of the ventral midbrain tegmentum were retrogradely labeled; most of the retrogradely labeled neurons also showed catecholamine fluorescence. However, some labeled cells (10-15%) did not show any catecholamine fluorescence. The present findings confirm the existence of a non-dopaminergic (DA) mesencephalo-cortical pathway and describe the topographical interrelationships between its DA and the non-DA cell bodies of origin.