title: Vasopressin-induced constriction of the isolated rat occipital artery is segment dependent.
abstract: BACKGROUND
  Circulating factors delivered to the nodose ganglion (NG) by the occipital artery (OA) have been shown to affect vagal afferent activity, and thus the contractile state of the OA may influence blood flow to the NG.
  
  
  METHODS
  OA were isolated and bisected into proximal and distal segments relative to the external carotid artery.
  
  
  RESULTS
  Bisection highlighted stark differences between maximal contractile responses and OA sensitivity. Specifically, maximum responses to vasopressin and the V1 receptor agonist were significantly higher in distal than proximal segments. Distal segments were significantly more sensitive to 5-hydroxytryptamine (5-HT) and the 5-HT2 receptor agonist than proximal segments. Angiotensin II (AT)2, V2 and 5-HT(1B/1D) receptor agonists did not elicit vascular responses. Additionally, AT1 receptor agonists elicited mild, yet not significantly different maximal responses between segments.
  
  
  CONCLUSIONS
  The results of this study are consistent with contractile properties of rat OA being mediated via AT1, V1 and 5-HT2 receptors and dependent upon the OA segment. Furthermore, vasopressin-induced constriction of the OA, regardless of a bolus dose or a first and second concentration-response curve, retained this unique segmental difference. We hypothesize that these segmental differences may be important in the regulation of blood flow through the OA in health and disease.
authors.affiliation: Department of Cardiology, Johns Hopkins University School of Medicine, Baltimore, Md., USA.
authors.forename: Stephen P
authors.initials: SP
authors.lastname: Chelko
authors.forename: Chad W
authors.initials: CW
authors.lastname: Schmiedt
authors.forename: Tristan H
authors.initials: TH
authors.lastname: Lewis
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Lewis
authors.forename: Tom P
authors.initials: TP
authors.lastname: Robertson
mesh_terms: D047228:Angiotensin II Type 1 Receptor Blockers / Q000494:pharmacology; D000818:Animals; D001127:Arginine Vasopressin / Q000494:pharmacology*; D002536:Cerebral Arteries / Q000033:anatomy & histology / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D006727:Hormone Antagonists / Q000494:pharmacology; D008297:Male; D009620:Nodose Ganglion / Q000098:blood supply*; D009778:Occipital Lobe / Q000098:blood supply*; D051381:Rats; D017207:Rats, Sprague-Dawley; D044140:Receptor, Angiotensin, Type 1 / Q000187:drug effects / Q000378:metabolism; D044348:Receptors, Serotonin, 5-HT2 / Q000187:drug effects / Q000378:metabolism; D017483:Receptors, Vasopressin / Q000187:drug effects / Q000378:metabolism; D012702:Serotonin Antagonists / Q000494:pharmacology; D017366:Serotonin Receptor Agonists / Q000494:pharmacology; D014661:Vasoconstriction / Q000187:drug effects*; D014662:Vasoconstrictor Agents / Q000494:pharmacology*
chemical_list: D047228:Angiotensin II Type 1 Receptor Blockers; D006727:Hormone Antagonists; D044140:Receptor, Angiotensin, Type 1; D044348:Receptors, Serotonin, 5-HT2; D017483:Receptors, Vasopressin; D012702:Serotonin Antagonists; D017366:Serotonin Receptor Agonists; D014662:Vasoconstrictor Agents; D001127:Arginine Vasopressin