title: Orexinergic fibers are in contact with Kölliker-Fuse nucleus neurons projecting to the respiration-related nuclei in the medulla oblongata and spinal cord of the rat.
abstract: The neural pathways underlying the respiratory variation dependent on vigilance states remain unsettled. In the present study, we examined the orexinergic innervation of Kölliker-Fuse nucleus (KFN) neurons sending their axons to the rostral ventral respiratory group (rVRG) and phrenic nucleus (PhN) as well as to the hypoglossal nucleus (HGN) by using a combined retrograde tracing and immunohistochemistry. After injection of cholera toxin B subunit (CTb) into the KFN, CTb-labeled neurons that are also immunoreactive for orexin (ORX) were found prominently in the perifornical and medial regions and additionally in the lateral region of the hypothalamic ORX field. After injection of fluorogold (FG) into the rVRG, PhN or HGN, we found an overlapping distribution of ORX-immunoreactive axon terminals and FG-labeled neurons in the KFN. Within the neuropil of the KFN, asymmetrical synaptic contacts were made between these terminals and neurons. We further demonstrated that many neurons labeled with FG injected into the rVRG, PhN, or HGN are immunoreactive for ORX receptor 2. Present data suggest that rVRG-, PhN- and HGN-projecting KFN neurons may be under the excitatory influence of the ORXergic neurons for the state-dependent regulation of respiration.
authors.affiliation: Department of Anatomy and Morphological Neuroscience, Shimane University School of Medicine, Izumo 693-8501, Japan.
authors.forename: Shigefumi
authors.initials: S
authors.lastname: Yokota
authors.affiliation: Department of Anatomy and Morphological Neuroscience, Shimane University School of Medicine, Izumo 693-8501, Japan.
authors.forename: Tatsuro
authors.initials: T
authors.lastname: Oka
authors.affiliation: Department of Anatomy and Morphological Neuroscience, Shimane University School of Medicine, Izumo 693-8501, Japan.
authors.forename: Hirohiko
authors.initials: H
authors.lastname: Asano
authors.affiliation: Department of Anatomy and Morphological Neuroscience, Shimane University School of Medicine, Izumo 693-8501, Japan. Electronic address: yyasui@med.shimane-u.ac.jp.
authors.forename: Yukihiko
authors.initials: Y
authors.lastname: Yasui
mesh_terms: D000818:Animals; D001369:Axons / Q000378:metabolism; D066193:Cervical Cord / Q000166:cytology* / Q000378:metabolism; D007031:Hypothalamus / Q000166:cytology; D007150:Immunohistochemistry; D065836:Kolliker-Fuse Nucleus / Q000166:cytology* / Q000648:ultrastructure; D008297:Male; D008526:Medulla Oblongata / Q000166:cytology* / Q000378:metabolism; D009434:Neural Pathways / Q000166:cytology / Q000378:metabolism; D056347:Neuroanatomical Tract-Tracing Techniques; D009474:Neurons / Q000166:cytology* / Q000378:metabolism; D064446:Orexin Receptors / Q000378:metabolism; D000068797:Orexins / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D012119:Respiration; D013116:Spinal Cord / Q000166:cytology* / Q000378:metabolism
chemical_list: D064446:Orexin Receptors; D000068797:Orexins
keywords: Hypoglossal nucleus; Kölliker-Fuse nucleus; Orexin; Orexin receptor 2; Parabrachial complex; Phrenic nucleus; Rat; Rostral ventral respiratory group