Expression of Group I metabotropic glutamate receptors on phenotypically different cells within the nucleus of the solitary tract in the rat

Neuroscience. 2009 Mar 17;159(2):701-16. doi: 10.1016/j.neuroscience.2008.09.060. Epub 2008 Oct 17.


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.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, N.I.H., Intramural

MeSH terms

  • Analysis of Variance
  • Animals
  • Blood Pressure / drug effects
  • Brain Mapping
  • Cell Count / methods
  • Glutamate Decarboxylase / metabolism
  • Heart Rate / drug effects
  • In Vitro Techniques
  • Male
  • Neural Pathways / physiology
  • Neurons / cytology*
  • Neurons / metabolism*
  • Nitric Oxide Synthase Type I / metabolism
  • Rats
  • Rats, Sprague-Dawley
  • Receptors, Metabotropic Glutamate / metabolism*
  • Solitary Nucleus / cytology*
  • Solitary Nucleus / drug effects
  • Stilbamidines / metabolism
  • Tyrosine 3-Monooxygenase / metabolism


  • 2-hydroxy-4,4'-diamidinostilbene, methanesulfonate salt
  • Receptors, Metabotropic Glutamate
  • Stilbamidines
  • metabotropic glutamate receptor type 1
  • Nitric Oxide Synthase Type I
  • Tyrosine 3-Monooxygenase
  • Glutamate Decarboxylase
  • glutamate decarboxylase 1