Combined immunocytochemical and radioautographic study of dopaminergic terminals in the neostriatum

Immunocytochemical localization of tyrosine hydroxylase alone or in combination with radioautographic localization of 3H-dopamine is used to determine the ultrastructural morphology and synaptic specializations of dopaminergic terminals in the n. caudatus-putamen (neostriatum) of adult rat brain. In all regions of the neostriatum, the enzyme immunoreactivity is localized to unmyelinated axons and axon terminals having a diameter of 0.1–1.5 µm. The most prevalent type of terminal is 0.15-0.8µm in diameter and forms symmetric junctions with unlabeled dendrites and dendritic spines. In ventricular regions, the tyrosine hydroxylase labeled axon terminals exhibit selective radioautographic labeling for 3H-dopamine, thus establishing the specificity of uptake and synthesis mechanisms within the same axons.