title: N-methyl-D-aspartate receptor activation in the neostriatum increases c-fos and fos-related antigens selectively in medium-sized neurons.
abstract: In the neostriatum a selective loss of neurons occurs following exposure to N-methyl-D-aspartate receptor agonists. One hypothesis emerging from this observation is that an excitotoxic process via N-methyl-D-aspartate receptors may contribute to the pathogenesis of Huntington's disease, which is characterized by the loss of medium-sized neurons. However, whether there is a selective distribution of N-methyl-D-aspartate receptors in specific populations of neostriatal neurons is unknown. In this study the expression of c-fos mRNA and protein was used to examine the response of neostriatal cells to N-methyl-D-aspartate receptor stimulation in the rat. After intrastriatal injection of the N-methyl-D-aspartate receptor agonist, quinolinic acid, an increase in c-fos mRNA concentrations was detected using in situ hybridization and Northern blot analysis. Western blot analysis showed that not only the c-Fos mRNA protein product but also other Fos-related antigens capable of binding to DNA were increased in response to N-methyl-D-aspartate receptor activation. The selectivity of the neuronal response to N-methyl-D-aspartate receptor activation was examined immunohistochemically at the light and ultrastructural levels. Our results indicate that N-methyl-D-aspartate receptor activation by quinolinic acid stimulates medium spiny neurons to increase c-Fos expression; to a lesser extent, medium aspiny interneurons and glial cells also respond. In contrast, negligible change in c-Fos expression is observed in large neurons. These results are consistent with other evidence that medium-sized spiny neurons are preferentially vulnerable to the toxic effects of excitatory amino acids acting at N-methyl-D-aspartate receptors. An additional implication of these findings is that activation of the N-methyl-D-aspartate receptor in medium spiny neurons leads to increased expression of candidate AP-1 transcription factors, thereby coupling the N-methyl-D-aspartate receptor and regulation of gene expression in signal transduction processes of the neostriatal medium spiny neuron.
authors.affiliation: Department of Medicine, University of Massachusetts Medical School, Worcester 01655.
authors.forename: N
authors.initials: N
authors.lastname: Aronin
authors.forename: K
authors.initials: K
authors.lastname: Chase
authors.forename: S M
authors.initials: SM
authors.lastname: Sagar
authors.forename: F R
authors.initials: FR
authors.lastname: Sharp
authors.forename: M
authors.initials: M
authors.lastname: DiFiglia
mesh_terms: D000818:Animals; D000941:Antigens / Q000032:analysis*; D001921:Brain / Q000378:metabolism; D003342:Corpus Striatum / Q000276:immunology / Q000378:metabolism*; D007267:Injections; D008297:Male; D008854:Microscopy, Electron; D009474:Neurons / Q000276:immunology / Q000378:metabolism*; D009693:Nucleic Acid Hybridization; D016760:Proto-Oncogene Proteins c-fos / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D017378:Quinolinic Acid; D011805:Quinolinic Acids / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D016194:Receptors, N-Methyl-D-Aspartate / Q000502:physiology*; D014018:Tissue Distribution
chemical_list: D000941:Antigens; D016760:Proto-Oncogene Proteins c-fos; D011805:Quinolinic Acids; D016194:Receptors, N-Methyl-D-Aspartate; D017378:Quinolinic Acid