title: Internal pallidum and substantia nigra control different parts of the mesopontine reticular formation in primate.
abstract: The locomotor area has recently emerged as a target for deep brain stimulation to lessen gait disturbances in advanced parkinsonian patients. An important step in choosing this target is to define anatomical limits of its 2 components, the pedunculopontine nucleus and the cuneiform nucleus, their connections with the basal ganglia, and their output descending pathway. Based on the hypothesis that pedunculopontine nucleus controls locomotion whereas cuneiform nucleus controls axial posture, we analyzed whether both nuclei receive inputs from the internal pallidum and substantia nigra using anterograde and retrograde tract tracing in monkeys. We also examined whether these nuclei convey descending projections to the reticulospinal pathway. Pallidal terminals were densely distributed and restricted to the pedunculopontine nucleus, whereas nigral terminals were diffusely observed in the whole extent of both the pedunculopontine nucleus and the cuneiform nucleus. Moreover, nigral terminals formed symmetric synapses with pedunculopontine nucleus and cuneiform nucleus dendrites. Retrograde tracing experiments confirmed these results because labeled cell bodies were observed in both the internal pallidum and substantia nigra after pedunculopontine nucleus injection, but only in the substantia nigra after cuneiform nucleus injection. Furthermore, anterograde tracing experiments revealed that the pedunculopontine nucleus and cuneiform nucleus project to large portions of the pontomedullary reticular formation. This is the first anatomical evidence that the internal pallidum and the substantia nigra control different parts of the brain stem and can modulate the descending reticulospinal pathway in primates. These findings support the functional hypothesis that the nigro-cuneiform nucleus pathway could control axial posture whereas the pallido-pedunculopontine nucleus pathway could modulate locomotion.
authors.affiliation: Université Pierre et Marie Curie-Paris 6, CR-ICM, UMR-S975, INSERM, U975, CNRS, UMR 7225, Assistance Publique-Hôpitaux de Paris, Groupe Pitié-Salpêtrière, Paris, France.
authors.forename: Anne-Sophie
authors.initials: AS
authors.lastname: Rolland
authors.forename: Carine
authors.initials: C
authors.lastname: Karachi
authors.forename: Marie-Paule
authors.initials: MP
authors.lastname: Muriel
authors.forename: Etienne C
authors.initials: EC
authors.lastname: Hirsch
authors.forename: Chantal
authors.initials: C
authors.lastname: François
mesh_terms: D000818:Animals; D001710:Biotin / Q000031:analogs & derivatives / Q000378:metabolism; D003911:Dextrans / Q000378:metabolism; D005917:Globus Pallidus / Q000502:physiology*; D008297:Male; D046529:Microscopy, Electron, Transmission / Q000379:methods; D009434:Neural Pathways / Q000378:metabolism / Q000502:physiology*; D011323:Primates; D012154:Reticular Formation / Q000033:anatomy & histology / Q000502:physiology*; D013378:Substantia Nigra / Q000502:physiology*; D018998:Wheat Germ Agglutinin-Horseradish Peroxidase Conjugate / Q000378:metabolism
chemical_list: D003911:Dextrans; D018998:Wheat Germ Agglutinin-Horseradish Peroxidase Conjugate; C076397:biotinylated dextran amine; D001710:Biotin