title: Role of glutamate receptors in the dorsal reticular nucleus in formalin-induced secondary allodynia.
abstract: The role of glutamate receptors present in the medullary dorsal reticular nucleus (DRt) in the formalin test and formalin-induced secondary nociception was studied in rats. Secondary mechanical allodynia was assessed with von Frey filaments applied to the rat's hindpaw, and secondary thermal hyperalgesia was evaluated with the tail-immersion test. The selective glutamate receptor antagonists MK801 (N-methyl-D-aspartate receptor antagonist), 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) (AMPA/KA receptor antagonist) and A841720 (metabotropic glutamate 1 receptor antagonist) were injected into the DRt before or 6 days after formalin injection in the rat. In the formalin test, the three antagonists significantly reduced the number of flinches in both phases of the test. DRt microinjection of MK801 or A841720, but not of CNQX, reduced both secondary nociceptive behaviors. Moreover, pre-treatment with the three antagonists injected into the DRt prevented the development of secondary mechanical allodynia and secondary thermal hyperalgesia. Similarly, in these rats, the number of c-Fos-like immunoreactive neurons were markedly reduced in both the superficial and deep lamina of the dorsal horn. Our findings support the role of DRt as a pain facilitator in acute and chronic pain states, and suggest a key role of glutamate receptors during the development and maintenance of formalin-induced secondary allodynia.
authors.affiliation: División de Neurociencias, Departamento de Neuropatología Molecular, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, México DF, México.
authors.forename: Mónica
authors.initials: M
authors.lastname: Ambriz-Tututi
authors.affiliation: División de Neurociencias, Departamento de Neuropatología Molecular, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, México D.F, México.
authors.forename: Marcela
authors.initials: M
authors.lastname: Palomero-Rivero
authors.affiliation: División de Neurociencias, Departamento de Neuropatología Molecular, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, México D.F, México.
authors.forename: Fernanda
authors.initials: F
authors.lastname: Ramirez-López
authors.affiliation: División de Neurociencias, Departamento de Neuropatología Molecular, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, México D.F, México.
authors.forename: Diana
authors.initials: D
authors.lastname: Millán-Aldaco
authors.affiliation: División de Neurociencias, Departamento de Neuropatología Molecular, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, México D.F, México.
authors.forename: And René
authors.initials: AR
authors.lastname: Drucker-Colín
mesh_terms: D018750:6-Cyano-7-nitroquinoxaline-2,3-dione / Q000494:pharmacology; D000818:Animals; D016291:Dizocilpine Maleate / Q000494:pharmacology; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D005260:Female; D005557:Formaldehyde; D006575:Heterocyclic Compounds, 3-Ring / Q000494:pharmacology; D006358:Hot Temperature; D006930:Hyperalgesia / Q000188:drug therapy / Q000378:metabolism*; D007150:Immunohistochemistry; D009474:Neurons / Q000187:drug effects / Q000378:metabolism; D059225:Nociception / Q000187:drug effects / Q000502:physiology; D010147:Pain Measurement; D016760:Proto-Oncogene Proteins c-fos / Q000378:metabolism; D017208:Rats, Wistar; D017470:Receptors, Glutamate / Q000378:metabolism*; D012154:Reticular Formation / Q000187:drug effects / Q000378:metabolism*; D014110:Touch
chemical_list: C516995:A-841720; D018691:Excitatory Amino Acid Antagonists; D006575:Heterocyclic Compounds, 3-Ring; D016760:Proto-Oncogene Proteins c-fos; D017470:Receptors, Glutamate; D005557:Formaldehyde; D016291:Dizocilpine Maleate; D018750:6-Cyano-7-nitroquinoxaline-2,3-dione
keywords: descending facilitation; dorsal reticular nucleus; glutamate receptors; rat; secondary allodynia