CONNECTIVITY OF THE LOBUS PAROLFACTORIUS OF THE DOMESTIC CHICKEN (GALLUS-DOMESTICUS) - AN ANTEROGRADE AND RETROGRADE PATHWAY TRACING STUDY

In 1-week-old domestic chicks, the connectivity of the lobus parolfact orius (LPO), part of the avian basal ganglia, was investigated using P haseolus vulgaris leucoagglutinin and horseradish peroxidase for anter ograde and retrograde pathway tracing, respectively. Tyrosine hydroxyl ase immunocytochemistry was applied in combination with Phaseolus lect in to assess the overlap between LPO efferents and diencephalic and me sencephalic catecholamine centres. Anterograde projections from LPO we re detected in the hyperstriatum, neostriatum, and paleostriatum. Intr anuclear connections were also apparent within the LPO. Descending LPO efferents innervated the lateral mammillary and intramedial nuclei an d the dorsomedial thalamic complex. Fibres from LPO were observed in t he tectal gray, substantia nigra, area ventralis tegmentalis of Tsai, and the adjacent nucleus mesencephalicus profundus. Further caudally, projections from LPO reached the nucleus papillioformis, locus coerule us, and subcoeruleus ventralis. LPO efferents were coextensive with ty rosine hydroxylase-positive cells in the nuclei mamillaris lateralis a nd intramedialis of the hypothalamus, area ventralis tegmentalis, subs tantia nigra, locus coeruleus, and subcoeruleus ventralis of mesenceph alic and pontine tegmentum. Close contacts between LPO fibres and cate cholamine cells were visible in the nigra and the area ventralis tegme ntalis. Retrograde labelling from LPO was found in the archistriatum, dorsomedial thalamic complex, nuclei lateralis anterior and superficia lis parvicellularis thalami, substantia nigra, central gray, area vent ralis tegmentalis of Tsai, and locus coeruleus and in cells dorsal to the decussation of brachium conjunctivum. Reciprocal connections were verified between the LPO and the following areas: dorsomedial thalamic complex, central gray, substantia nigra, area ventralis of Tsai, and locus coeruleus. (C) 1994 Wiley-Liss, Inc.