Enhanced dopamine cell survival in reaggregates containing telencephalic target cells

Dissociated, 14-day-old embryonic cells of the rostral mesencephalic tegmentum (RMT), including the dopamine neurons of this region, were allowed to reaggregate and develop in rotatory culture for 7 days in the presence of dissociated embryonic cells from the target areas of the dopaminergic neurons, corpus striatum (CS) or frontal cortex (FCx). Alternatively, RMT cells were allowed to reaggregate by themselves or in the presence of dissociated cells from a telencephalic area, occipital cortex (OCx), or mesencephalic area, tectum (T), which are not target areas for the dopamine neurons. Histofluorescence analysis revealed the number of dopamine neurons contained within reaggregates of any given type. Approximately 4 times as many dopamine neurons were found in RMT-CS coaggregates and 1.5 times as many in RMT-FCx coaggregates than in aggregates constituted from cells of the RMT either alone, or in coaggregates from RMT-OCx or RMT-T. Since axonal process formation and maintenance can only be observed in RMT-CS and RMT-FCx coaggregates, the enhanced dopamine neuron survival is probably due to an interaction of dopaminergic axonal processes with target cells within the reaggregates.