Selective association of dopamine axons with their striatal target cells in vitro

The purpose of the present study was to examine the distribution of dopamine (DA) axons after simultaneously confronting DA cells with both target cells of the corpus striatum (CS) and with non-target cells of the tectum (T). Dissociated fetal cells of rostral mesencephalic tegmentum (RMT) containing DA neurons and dissociated non-target tectal cells were exposed to wheat germ agglutinin conjugated to the fluorescent dye, rhodamine, prior to reaggregation in rotatory culture in order to distinguish these cells from non-dyed CS cells in the resulting reaggregates. After 9 days in culture, RMT-T-CS reaggregates were exposed to 10(-5)M DA and processed for DA-fluorescence histochemistry. Single reaggregates were serially sectioned and color photomicrographs prepared from each section. It was found that non-target cells (red rhodamine fluorescence) segregated from the undyed target cells, forming discrete areas containing the two cell types. DA nerve cell bodies and their processes could be distinguished by their green fluorescence. Since it is not possible to distinguish axonal from dendritic processes in a single section, the extent of neuronal dendritic arborization was estimated from reaggregates prepared from cells of the RMT and non-target T cells, in which there is no extensive proliferation of DA axons and fluorescent DA processes (presumably dendrites) are confined to the area near the cell body. Following exclusion of DA dendritic fluorescence, it was found that 85.2% of the presumed axonal fibers were present in the non-dyed areas containing striatal target cells.(ABSTRACT TRUNCATED AT 250 WORDS)