SOME CHARACTERISTICS OF RAT NIGROSTRIATAL DOPAMINERGIC NEUROCONNECTION DURING DEVELOPMENT——A COMBINED IMMUNOCYTOCHEMICAL AND ELECTRON-MICROSCOPIC STUDY

The characteristics of the nigrostriatal dopaminergic neuroconnections in developing rats are studied by combined immunocytochemical and electron-microscopic techniques, with an antibody to tyrosine hydroxylase (TH). From the embryonic day 21 on, some of the THpositive nerve fibers are densely packed in the striatum to form a patch-like dopamine island. The percentage of the TH-positive nerve terminals among the labeled profiles is much higher inside than outside the dopamine island (P<0.01). On the other hand, the TH-positive terminals mainly form symmetrical axon-dendritic synapses, while most of the TH-negative terminals form asymmetrical axon-spinous synapses. The functional significance of the characterized dopaminergic connection is discussed.