Immunocytochemical evidence for direct connections between neurotensin-containing axons and dopaminergic neurons in the rat ventral midbrain tegmentum.

A light- and electron-microscopic double antigen localization technique was employed to study cellular relationships between neurotensin (NT)-containing axons and dopaminergic neurons in the substantia nigra and ventral tegmental area of the rat. Direct contacts were observed between NT-immunoreactive axon terminals and the dendrites and perikarya of neurons containing the dopamine biosynthetic enzyme, tyrosine hydroxylase (TH). NT-positive terminals were also found to contact unlabeled dendrites and neuronal somata. These results reveal an ultrastructural substrate through which endogenous NT might influence the activity of dopaminergic neurons in the ventral midbrain tegmentum.