title: Non-serotonergic midbrain neurons are involved in picrotoxin-induced analgesia. An immunohistochemical study in the rat.
abstract: Intravenous picrotoxin inhibits spinal nociceptive neurons through disinhibitory activation of neurons in the periaqueductal gray (PAG) and nucleus raphe dorsalis (NRD), where the descending antinociceptive system arises. We found Fos-like immunoreactivity in PAG/NRD neurons after intravenous injection of picrotoxin. This distribution of c-Fos expression is consistent with a role of PAG/NRD for antinociception; neurons with intense Fos-like immunoreactivity was also clustered in the Edinger-Westphal nucleus (EW). Double fluorescence immunohistochemistry for c-Fos and serotonin revealed that PAG/NRD/EW neurons expressing c-Fos were non-serotonergic. These data suggest that non-serotonergic PAG/NRD/EW neurons are involved in the picrotoxin-induced analgesia.
authors.affiliation: Department of Physiology, Shiga University of Medical Science, 520-2192, Otsu, Japan. koyama@belle.shiga-med.ac.jp
authors.forename: N
authors.initials: N
authors.lastname: Koyama
authors.forename: T
authors.initials: T
authors.lastname: Nishio
authors.forename: T
authors.initials: T
authors.lastname: Yokota
mesh_terms: D000698:Analgesia; D000818:Animals; D007150:Immunohistochemistry; D007275:Injections, Intravenous; D008297:Male; D008636:Mesencephalon / Q000166:cytology / Q000187:drug effects*; D009474:Neurons / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D009802:Oculomotor Nerve / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D010487:Periaqueductal Gray / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D010852:Picrotoxin / Q000008:administration & dosage*; D016760:Proto-Oncogene Proteins c-fos / Q000378:metabolism*; D011903:Raphe Nuclei / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D012701:Serotonin / Q000378:metabolism*
chemical_list: D010852:Picrotoxin; D016760:Proto-Oncogene Proteins c-fos; D012701:Serotonin