title: Neurokinin-1 and neurokinin-3 receptors in primate substantia nigra.
abstract: Striatonigral axons co-release GABA and substance P (SP) at their target sites, but little is known about the action of SP at nigral level. Therefore, we studied immunohistochemically the cellular and subcellular localization of SP and its high affinity receptors neurokinin-1 (NK-1R) and neurokinin-3 (NK-3R) at nigral level in squirrel monkeys. Immunofluorescent studies revealed that, although SP+ fibers arborised more densely in the pars reticulata (SNr) than in the pars compacta (SNc), the two nigral divisions harbored numerous neurons expressing NK-1R and NK-3R. Confocal microscopic analyses showed that numerous SNr neurons and virtually all SNc dopaminergic neurons contained both NK-1R and NK-3R. At the electron microscope level, NK-1R and NK-3R were mainly associated with intracellular sites or located at extrasynaptic position on plasma membrane. A small proportion of SP+ boutons also showed NK-3R immunoreactivity. The distribution of NK-1R and NK-3R in SNr and SNc suggests that SP exerts its effect through postsynaptic receptors, as well as via presynaptic autoreceptors and heteroreceptors. These findings indicate that the excitatory peptide SP can modulate the inhibitory action of GABA at nigral level and suggest that the co-release of these two neuroactive substances should be taken into account when considering the functional organization of the basal ganglia.
authors.affiliation: Centre de recherche Université Laval Robert-Giffard 2601, Chemin de la Canardière, Local F-6500 Beauport, Québec, Canada.
authors.forename: Martin
authors.initials: M
authors.lastname: Lévesque
authors.forename: Marie-Josée
authors.initials: MJ
authors.lastname: Wallman
authors.forename: Remy
authors.initials: R
authors.lastname: Parent
authors.forename: Attila
authors.initials: A
authors.lastname: Sík
authors.forename: André
authors.initials: A
authors.lastname: Parent
mesh_terms: D000818:Animals; D017660:Autoreceptors / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism* / Q000648:ultrastructure; D003342:Corpus Striatum / Q000378:metabolism / Q000648:ultrastructure; D004298:Dopamine / Q000378:metabolism; D005260:Female; D005455:Fluorescent Antibody Technique; D008297:Male; D018613:Microscopy, Confocal; D016253:Microscopy, Immunoelectron; D009433:Neural Inhibition / Q000502:physiology; D009434:Neural Pathways / Q000378:metabolism / Q000648:ultrastructure; D009474:Neurons / Q000378:metabolism*; D017729:Presynaptic Terminals / Q000378:metabolism; D018040:Receptors, Neurokinin-1 / Q000378:metabolism*; D018042:Receptors, Neurokinin-3 / Q000378:metabolism*; D012453:Saimiri; D013373:Substance P / Q000378:metabolism*; D013378:Substantia Nigra / Q000033:anatomy & histology / Q000378:metabolism*; D013570:Synaptic Membranes / Q000378:metabolism / Q000648:ultrastructure; D009435:Synaptic Transmission / Q000502:physiology; D005680:gamma-Aminobutyric Acid / Q000378:metabolism
chemical_list: D017660:Autoreceptors; D018040:Receptors, Neurokinin-1; D018042:Receptors, Neurokinin-3; D013373:Substance P; D005680:gamma-Aminobutyric Acid; D004298:Dopamine