title: Expression of Group I metabotropic glutamate receptors on phenotypically different cells within the nucleus of the solitary tract in the rat.
abstract: Group I metabotropic glutamate receptors (mGluRs) are G-coupled receptors that modulate synaptic activity. Previous studies have shown that Group I mGluRs are present in the nucleus of the solitary tract (NTS), in which many visceral afferents terminate. Microinjection of selective Group I mGluR agonists into the NTS results in a depressor response and decrease in sympathetic nerve activity. There is, however, little evidence detailing which phenotypes of neurons within the NTS express Group I mGluRs. In brainstem slices, we performed immunohistochemical localization of Group I mGluRs and either glutamic acid decarboxylase 67 kDa isoform (GAD67), neuronal nitric oxide synthase (nNOS) or tyrosine hydroxylase (TH). Fluoro-Gold (FG, 2%; 15 nl) was microinjected in the caudal ventrolateral medulla (CVLM) of the rat to retrogradely label NTS neurons that project to CVLM. Group I mGluRs were distributed throughout the rostral-caudal extent of the NTS and were found within most NTS subregions. The relative percentages of Group I mGluR expressing neurons colabeled with the different markers were FG (6.9+/-0.7) nNOS (5.6+/-0.9), TH (3.9+/-1.0), and GAD67 (3.1+/-1.4). The percentage of FG containing cells colabeled with Group I mGluR (13.6+/-2.0) was greater than the percent colabeled with GAD67 (3.1+/-0.5), nNOS (4.7+/-0.5), and TH (0.1+/-0.08). Cells triple labeled for FG, nNOS, and Group I mGluRs were identified in the NTS. Thus, these data provide an anatomical substrate by which Group I mGluRs could modulate activity of CVLM projecting neurons in the NTS.
authors.affiliation: Department of Medical Pharmacology and Physiology, University of Missouri, Columbia, MO 65211, USA.
authors.forename: J R
authors.initials: JR
authors.lastname: Austgen
authors.forename: A Y
authors.initials: AY
authors.lastname: Fong
authors.forename: C M
authors.initials: CM
authors.lastname: Foley
authors.forename: P J
authors.initials: PJ
authors.lastname: Mueller
authors.forename: D D
authors.initials: DD
authors.lastname: Kline
authors.forename: C M
authors.initials: CM
authors.lastname: Heesch
authors.forename: E M
authors.initials: EM
authors.lastname: Hasser
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D001931:Brain Mapping; D002452:Cell Count / Q000379:methods; D005968:Glutamate Decarboxylase / Q000378:metabolism; D006339:Heart Rate / Q000187:drug effects; D066298:In Vitro Techniques; D008297:Male; D009434:Neural Pathways / Q000502:physiology; D009474:Neurons / Q000166:cytology* / Q000378:metabolism*; D052248:Nitric Oxide Synthase Type I / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D018094:Receptors, Metabotropic Glutamate / Q000378:metabolism*; D017552:Solitary Nucleus / Q000166:cytology* / Q000187:drug effects; D013266:Stilbamidines / Q000378:metabolism; D014446:Tyrosine 3-Monooxygenase / Q000378:metabolism
chemical_list: C049774:2-hydroxy-4,4'-diamidinostilbene, methanesulfonate salt; D018094:Receptors, Metabotropic Glutamate; D013266:Stilbamidines; C104077:metabotropic glutamate receptor type 1; D052248:Nitric Oxide Synthase Type I; D014446:Tyrosine 3-Monooxygenase; D005968:Glutamate Decarboxylase; C402565:glutamate decarboxylase 1