Single neurons in the ventral tegmental area that project to both the cerebral and cerebellar cortical areas by way of axon collaterals.

Recently, we have found that the ventral tegmental area of the rat sends dopaminergic and non-dopaminergic axons, respectively, to the cerebellar cortex and deep cerebellar nuclei [Ikai et al. (1992) Neuroscience 51, 719-728]. In the present study, employing fluorescent retrograde double labeling with Fast Blue and Diamidino Yellow, we examined whether individual neurons in the ventral tegmental area of the rat send their axons to both the cerebellum and other brain regions. The neurons projecting to the cerebellar cortex often issued axon collaterals to the cerebral cortical areas, including the prelimbic-anterior cingulate cortices and piriform-entorhinal cortices, but not so frequently to the subcortical regions, including the nucleus accumbens, lateral septum, amygdala, and lateral habenula. On the other hand, the neurons projecting to the deep cerebellar nuclei rarely sent axon collaterals to the cerebral cortical and subcortical regions.