title: Thioperamide, a histamine H3-receptor blocker, facilitates vasopressor response to footshocks.
abstract: OBJECTIVE
  We assessed the functional role of the histamine H3-receptor in conscious intact rats during activation of the sympathoadrenal axis.
  
  
  METHODS
  Male Sprague-Dawley rats, with or without cerebroventricular cannula, were subjected to mild footshocks and mean arterial pressure (MAP) and heart rate were determined using a tail-cuff plethysmograph.
  
  
  METHODS
  Saline, phentolamine (3 mg/kg, i.p.), (R)-alphafluoromethylhistidine (AFMH) (100 mg/kg, i.p., or 100 microg/5 microl, i.v.t.), (R)-alphamethylhistamine (AMH) (2 mg/kg, i.p. or 100 microg/5 microl, i.v.t.), thioperamide (THIO) (1 or 2 mg/kg, i.p., or 100 microg/5 microl, i.v.t.), mepyramine (10 mg/kg, i.p.), cimetidine (2 mg/kg, i.p.).
  
  
  METHODS
  Urinary catecholamines were determined by fluorometry. Statistical differences between experimental groups were evaluated by Student's t-test or one-way ANOVA.
  
  
  RESULTS
  Footshocks increased both MAP and heart rate. The vasopressor response to footshocks was facilitated (p < 0.001) by i.p. administration of AFMH, a histidine decarboxylase inhibitor, or THIO, a H3-receptor antagonist, but not by i.v.t. injection of these drugs. AMH, a H3-receptor agonist, given i.p., decreased the vasopressor response to footshocks (p < 0.001). This action of AMH was abolished by THIO but not by mepyramine or cimetidine. The MAP response to exogenous norepinephrine was not altered by i.p. administration of either AFMH or THIO.
  
  
  CONCLUSIONS
  Our results demonstrate an involvement of peripheral histamine H3 prejunctional receptors in the inhibitory modulation of peripheral noradrenergic responses during stress.
authors.affiliation: School of Pharmacy, Universidad Central de Venezuela, Caracas.
authors.forename: Y
authors.initials: Y
authors.lastname: Acuña
authors.forename: Y
authors.initials: Y
authors.lastname: Mathison
authors.forename: H A
authors.initials: HA
authors.lastname: Campos
authors.forename: A
authors.initials: A
authors.lastname: Israel
mesh_terms: D000818:Animals; D000959:Antihypertensive Agents / Q000494:pharmacology; D001794:Blood Pressure / Q000187:drug effects*; D002927:Cimetidine / Q000494:pharmacology; D004558:Electric Stimulation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006339:Heart Rate / Q000187:drug effects*; D006614:Hindlimb; D006633:Histamine Antagonists / Q000494:pharmacology*; D006634:Histamine H1 Antagonists / Q000494:pharmacology; D006635:Histamine H2 Antagonists / Q000494:pharmacology; D008297:Male; D008762:Methylhistidines / Q000494:pharmacology; D009638:Norepinephrine / Q000494:pharmacology; D010646:Phentolamine / Q000494:pharmacology; D010880:Piperidines / Q000494:pharmacology*; D011738:Pyrilamine / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D018100:Receptors, Histamine H3 / Q000187:drug effects*; D014662:Vasoconstrictor Agents / Q000494:pharmacology
chemical_list: D000959:Antihypertensive Agents; D004791:Enzyme Inhibitors; D006633:Histamine Antagonists; D006634:Histamine H1 Antagonists; D006635:Histamine H2 Antagonists; D008762:Methylhistidines; D010880:Piperidines; D018100:Receptors, Histamine H3; D014662:Vasoconstrictor Agents; C046181:alpha-methylhistidine; C028309:alpha-fluoromethylhistidine; D002927:Cimetidine; D011738:Pyrilamine; C052075:thioperamide; D009638:Norepinephrine; D010646:Phentolamine