title: Pressor and intestinal vascular bed responses to vasopressin after cholinergic blockade.
abstract: Superior mesenteric arterial flow, aortic blood pressure, and heart rate were recorded, and plasma arginine vasopressin (AVP) concentrations were measured in conscious unrestrained cats during intravenous infusions of AVP (0.1-8.1 mU.kg-1. min-1). Responses to AVP were studied when autonomic nervous system (ANS) function remained intact and when the cholinergic limb of the system had been antagonized by methscopolamine nitrate (0.5 mg/kg) or by pirenzepine (60 micrograms/kg). Elevations in the circulating levels of AVP to approximately 30 and 600 fmol/ml in cats with intact ANS function were associated with decreases in superior mesenteric arterial conductance (SMAC, ml.min-1.kg-1.mmHg-1) of approximately 9 and 50%. The relationship between the dose of AVP and the decreases in SMAC for methscopolamine-treated cats was displaced slightly but significantly to the left of that for intact cats. The relationship between the dose of AVP and the increases in arterial pressure for methscopolamine-treated cats was also significantly displaced to the left of that for intact cats; however, the magnitude of the displacement was much greater than that for the dose-conductance relationship. In contrast to the findings with methscopolamine, pirenzepine did not significantly influence either the dose-conductance or dose-blood pressure response curves. These results are consistent with three conclusions. First, physiologically (less than 30 fmol/ml) and pathophysiologically (less than 600 fmol/ml) relevant concentrations of AVP are capable of inducing intestinal vasoconstriction, even in the presence of intact autonomic function. Second, the cholinergic limb of the autonomic nervous system plays a major role in buffering the vasopressor effects of AVP.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Pharmacology, University of Saskatchewan, Saskatoon, Canada.
authors.forename: D S
authors.initials: DS
authors.lastname: Martin
authors.forename: J R
authors.initials: JR
authors.lastname: McNeill
mesh_terms: D000818:Animals; D001127:Arginine Vasopressin / Q000097:blood; D001794:Blood Pressure / Q000187:drug effects; D002415:Cats; D004305:Dose-Response Relationship, Drug; D004553:Electric Conductivity; D006339:Heart Rate / Q000187:drug effects; D007422:Intestines / Q000098:blood supply*; D019832:N-Methylscopolamine; D010890:Pirenzepine / Q000494:pharmacology; D012039:Regional Blood Flow; D012602:Scopolamine Derivatives / Q000494:pharmacology; D013152:Splanchnic Circulation; D014667:Vasopressins / Q000494:pharmacology*
chemical_list: D012602:Scopolamine Derivatives; D014667:Vasopressins; D001127:Arginine Vasopressin; D010890:Pirenzepine; D019832:N-Methylscopolamine