title: Histaminergic H3-Heteroreceptors as a Potential Mediator of Betahistine-Induced Increase in Cochlear Blood Flow.
abstract: OBJECTIVE
  Betahistine is a histamine-like drug that is considered beneficial in Ménière's disease by increasing cochlear blood flow. Acting as an agonist at the histamine H1-receptor and as an inverse agonist at the H3-receptor, these receptors as well as the adrenergic α2-receptor were investigated for betahistine effects on cochlear blood flow.
  
  
  METHODS
  A total of 54 Dunkin-Hartley guinea pigs were randomly assigned to one of nine groups treated with a selection of H1-, H3- or α2-selective agonists and antagonists together with betahistine. Cochlear blood flow and mean arterial pressure were recorded for 3 min before and 15 min after infusion.
  
  
  RESULTS
  Blockage of the H3- or α2-receptors caused a suppression of betahistine-mediated typical changes in cochlear blood flow or blood pressure. Activation of H3-receptors caused a drop in cochlear blood flow and blood pressure. H1-receptors showed no involvement in betahistine-mediated changes of cochlear blood flow.
  
  
  CONCLUSIONS
  Betahistine most likely affects cochlear blood flow through histaminergic H3-heteroreceptors.
authors.affiliation: Department of Otorhinolaryngology, Head and Neck Surgery, University of Gx00F6;ttingen Hospital, Gx00F6;ttingen, Germany.
authors.forename: Mattis
authors.initials: M
authors.lastname: Bertlich
authors.forename: Friedrich
authors.initials: F
authors.lastname: Ihler
authors.forename: Saskia
authors.initials: S
authors.lastname: Freytag
authors.forename: Bernhard G
authors.initials: BG
authors.lastname: Weiss
authors.forename: Michael
authors.initials: M
authors.lastname: Strupp
authors.forename: Martin
authors.initials: M
authors.lastname: Canis
mesh_terms: D000818:Animals; D001621:Betahistine / Q000494:pharmacology*; D003051:Cochlea / Q000098:blood supply* / Q000187:drug effects / Q000378:metabolism; D005260:Female; D006168:Guinea Pigs; D017442:Histamine Agonists / Q000494:pharmacology*; D006633:Histamine Antagonists / Q000494:pharmacology*; D018100:Receptors, Histamine H3 / Q000378:metabolism*; D012039:Regional Blood Flow / Q000187:drug effects* / Q000502:physiology
chemical_list: D017442:Histamine Agonists; D006633:Histamine Antagonists; D018100:Receptors, Histamine H3; D001621:Betahistine