title: Gene expression of ionotropic glutamate receptor subunits in the tectofugal pathway of the pigeon.
abstract: The tectofugal pathway in birds consists of four stations, the retina, optic tectum, rotundal nucleus, and entopallium, and it conveys visual information via three ascending pathways. These pathways consist of retino-tectal, tecto-rotundal and rotundo-entopallial cells, all of which are glutamatergic. The present study examined the localization of ionotropic glutamate receptors (iGluRs) to identify the target areas of glutamatergic projections in the tectofugal pathway in pigeons. Nine subunits of iGluRs were analyzed using in situ hybridization as follows: AMPA receptors (GluA1, GluA2, GluA3, and GluA4), kainate receptors (GluK1, GluK2, and GluK4), and NMDA receptors (GluN1 and GluN2A). Hybridization signals of subunits showed various intensities in different cells. In the optic tectum, a strong to moderate expression was observed in layer 10 (GluA2, GluA3, GluK4, and GluN1) and layer 13 (GluA2, GluK4, GluN1, and GluN2A). The rotundal nucleus intensely expressed GluA3, GluA4, GluK1, and GluK4. In the entopallium, an intense to moderate expression of GluK1 and GluK4, and a moderate to weak expression of AMPA and NMDA receptors were observed. Furthermore, the parvocellular and magnocellular parts of the isthmic nuclei showed a strong expression of GluA2, GluA3, GluK4, and GluN1. The present findings demonstrate the expression of iGluRs in glutamatergic projection targets of the tectofugal pathway in birds and suggest a diversity of iGluRs in the transmission of visual information.
authors.affiliation: Laboratory of Veterinary Anatomy, Faculty of Applied Biological Sciences, Gifu University, Yanagido, Gifu 501-1193, Japan. Electronic address: atozi@gifu-u.ac.jp.
authors.forename: Y
authors.initials: Y
authors.lastname: Atoji
mesh_terms: D000818:Animals; D010856:Columbidae; D005260:Female; D015870:Gene Expression / Q000502:physiology*; D005968:Glutamate Decarboxylase / Q000235:genetics / Q000378:metabolism; D008297:Male; D021122:Protein Subunits / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D058468:Receptors, Ionotropic Glutamate / Q000235:genetics / Q000378:metabolism*; D012160:Retina / Q000033:anatomy & histology / Q000378:metabolism*; D013477:Superior Colliculi / Q000033:anatomy & histology / Q000378:metabolism*; D050599:Vesicular Glutamate Transport Protein 2 / Q000235:genetics / Q000378:metabolism; D014795:Visual Pathways / Q000502:physiology*
chemical_list: D021122:Protein Subunits; D012333:RNA, Messenger; D058468:Receptors, Ionotropic Glutamate; D050599:Vesicular Glutamate Transport Protein 2; D005968:Glutamate Decarboxylase; C401141:glutamate decarboxylase 2
keywords: AMPA receptor; GAD65; NMDA receptor; isthmic nucleus; kainate receptor; vGluT2