Isolated catecholaminergic projections from substantia nigra and locus coeruleus to caudate, hippocampus and cerebral cortex formed by intraocular sequential double brain grafts

Sequential intraocular grafting of defined areas from fetal rat brain to adult host rats was used to explore the possibility that such double grafts would become interconnected. Norepinephrine- containing neurons of the locus coeruleus were grafted together with either parietal cerebral cortex, hippocampus, or the caudate nucleus. Dopamine-containing neurons of the substantia nigra were transplanted together with either parietal cerebral cortex or the caudate nucleus. The brainstem grafts showed good survival and development in oculo, using both histochemical and electrophysiological criteria. Locus coeruleus neurons were found to innervate cerebral cortex, hippocampus, and the caudate nucleus. Substantia nigra neurons invaded cerebral cortex abundantly, with a terminal distribution typical of cortical DA terminals in situ. The innervation of the caudate nucleus from substantia nigra transplants was variable, but areas of dense confluent terminals were observed. We conclude that sequential brain grafting in oculo permits generation of isolated yet defined catecholaminergic projections, which are suitable for electrophysiological, pharmacological, and histochemical studies.