title: Contribution of anterior cingulate cortex and descending pain inhibitory system to analgesic effect of lemon odor in mice.
abstract: BACKGROUND
  Affections are thought to regulate pain perception through the descending pain inhibitory system in the central nervous system. In this study, we examined in mice the affective change by inhalation of the lemon oil, which is well used for aromatherapy, and the effect of lemon odor on pain sensation. We also examined the anterior cingulate cortex (ACC) and descending pain inhibitory system to such regulation of pain.
  
  
  RESULTS
  In the elevated plus maze, the time spent in the open arms was increased by inhalation of lemon oil. The pain behavior induced by injection of formalin into the hind paw was decreased. By inhalation of lemon oil, the number of c-Fos expression by formalin injection was significantly increased in the ACC, periaqueductal grey (PAG), nucleu raphe magnus (NRM) and locus ceruleus, and decreased in the spinal dorsal horn (SDH). The destruction of the ACC with ibotenic acid led to prevent the decrease of formalin-evoked nocifensive behavior in mice exposed to lemon oil. In these mice, the change of formalin-induced c-Fos expression in the ACC, lateral PAG, NRM and SDH by lemon odor was also prevented. Antagonize of dopamine D1 receptor in the ACC prevented to the analgesic effect of lemon oil.
  
  
  CONCLUSIONS
  These results suggest that the analgesic effect of lemon oil is induced by dopamine-related activation of ACC and the descending pain inhibitory system.
authors.affiliation: Department of Human and Artificial Intelligence Systems, Graduate School of Engineering, and Research and Education Program for Life Science, University of Fukui, 3-9-1 Bunkyo, 910-8507 Fukui, Japan. ikeda@u-fukui.ac.jp.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Ikeda
authors.forename: Syuntaro
authors.initials: S
authors.lastname: Takasu
authors.forename: Kazuyuki
authors.initials: K
authors.lastname: Murase
mesh_terms: D000280:Administration, Inhalation; D000339:Affect / Q000187:drug effects; D000818:Animals; D019341:Aromatherapy; D001552:Benzazepines / Q000494:pharmacology; D004195:Disease Models, Animal; D018492:Dopamine Antagonists / Q000494:pharmacology; D018690:Excitatory Amino Acid Agonists / Q000633:toxicity; D005106:Exploratory Behavior / Q000187:drug effects; D005557:Formaldehyde / Q000633:toxicity; D006179:Gyrus Cinguli / Q000187:drug effects / Q000293:injuries / Q000502:physiology*; D007051:Ibotenic Acid / Q000633:toxicity; D018782:Maze Learning / Q000187:drug effects; D051379:Mice; D008813:Mice, Inbred ICR; D009434:Neural Pathways / Q000502:physiology*; D009812:Odorants; D010146:Pain / Q000139:chemically induced / Q000188:drug therapy*; D010147:Pain Measurement; D010938:Plant Oils / Q000008:administration & dosage*
chemical_list: D001552:Benzazepines; D018492:Dopamine Antagonists; D018690:Excitatory Amino Acid Agonists; D010938:Plant Oils; C534628:SCH 23390; D005557:Formaldehyde; D007051:Ibotenic Acid; C501365:lemon oil