Explant cultures of dog substantia nigra and striatum: a model for the study of nigro-striatal dopamine neurons.

The development of organotypic co-cultures of substantia nigra and striatum from newborn dog brain was studied. Histofluorescence demonstrated the presence of catecholamine containing neurons in the substantia nigra. These neurons extended fluorescing processes that entered the striatum. High performance liquid chromatography identified the catecholamine as dopamine (DA). The DA was metabolized to homovanillic acid, which was accumulated in the feeding medium. The synthesis of DA was inhibited by the tyrosine hydroxylase inhibitor alpha-methyl tyrosine. The striatal tissue contained DA receptors, which increased during the development of the cultures. Electron microscopy demonstrated the presence of DA containing axons in the striatum; some of the axons established synaptic contacts with small dendritic branches. Several types of neurons could be identified in the striatum by electron microscopy. The presence of GABA in some striatal neurons was indicated by their ability to accumulate exogenous 3H-GABA. These observations suggest that the organotypic nigro-striatal cultures develop several of the characteristics of the same structures in the brain and therefore could be used as a model for the study of the DA containing neurons of the substantia nigra.