title: Spinal bombesin-recognized neurones mediate more nonhistaminergic than histaminergic sensation of itch in mice.
abstract: BACKGROUND
  There may be distinct pathways for transmission of histaminergic and nonhistaminergic itch, but all scratching behaviours elicited by histamine-dependent and histamine-independent pruritogens are diminished when spinal bombesin-recognized neurones are ablated.
  
  
  OBJECTIVE
  To investigate whether there is a difference in transmission of spinal itch signals between histamine-induced itch and nonhistamine-induced itch after neurotoxic destruction of spinal bombesin-recognized neurones.
  
  
  METHODS
  To ascertain the different relevance of spinal bombesin-recognized neurones in transmission of itch signals between these two classes of pruritogens, we determined the distribution of Fos-positive cells in the dorsal horn of spinal cord after stimulation with histamine (500 μg/site) and chloroquine (200 μg/site) in mice with spinal bombesin-recognized neurones ablated by intrathecal injection of bombesin-saporin (400 ng/5 μL).
  
  
  RESULTS
  We found that after stimulation with both histamine and chloroquine, fewer Fos-positive cells were present in mice treated with bombesin-saporin compared with those treated with saporin alone. The reduction in Fos expression was greater with chloroquine than with histamine, and the distribution of Fos-positive cells was also different. We used biotin-labelled isolectin (IB)4, which labels one subset of C-fibres, and found that the percentages of Fos-positive cells in three areas (the dorsal to IB4-labelled region, the IB4-labelled region itself, and the ventral to IB4-labelled region) all changed significantly after intradermal injection of chloroquine, but not histamine, in mice treated with bombesin-saporin.
  
  
  CONCLUSIONS
  These results suggest that spinal bombesin-recognized neurones are critical to both the histamine-dependent and histamine-independent pathways for itch, and that they mediate more nonhistaminergic than histaminergic sensation of itch in mice.
authors.affiliation: Department of Anaesthesiology, Shengjing Hospital of China Medical University, Shenyang, China. hanningsy@yahoo.com.cn
authors.forename: N
authors.initials: N
authors.lastname: Han
authors.forename: J Y
authors.initials: JY
authors.lastname: Zu
authors.forename: J
authors.initials: J
authors.lastname: Chai
mesh_terms: D000818:Animals; D001839:Bombesin / Q000008:administration & dosage; D002738:Chloroquine / Q000494:pharmacology; D003714:Denervation / Q000379:methods; D006632:Histamine / Q000494:pharmacology; D017442:Histamine Agonists / Q000494:pharmacology*; D006967:Hypersensitivity / Q000378:metabolism / Q000503:physiopathology; D007150:Immunohistochemistry; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018377:Neurotransmitter Agents / Q000008:administration & dosage; D020671:Posterior Horn Cells / Q000187:drug effects / Q000502:physiology*; D016760:Proto-Oncogene Proteins c-fos / Q000378:metabolism; D011537:Pruritus / Q000139:chemically induced / Q000503:physiopathology*; D018004:Receptors, Bombesin / Q000378:metabolism; D054789:Ribosome Inactivating Proteins, Type 1 / Q000008:administration & dosage; D000076985:Saporins; D012867:Skin / Q000294:innervation; D009435:Synaptic Transmission / Q000502:physiology
chemical_list: D017442:Histamine Agonists; D018377:Neurotransmitter Agents; D016760:Proto-Oncogene Proteins c-fos; D018004:Receptors, Bombesin; D054789:Ribosome Inactivating Proteins, Type 1; D006632:Histamine; D002738:Chloroquine; D000076985:Saporins; D001839:Bombesin