title: Inhibition of vasoconstriction by platelet activating factor in the in situ blood perfused rat mesentery.
abstract: 1. Perfusion pressure was measured in the in situ mesentery of anaesthetized rats perfused with blood at a constant 2 mL/min. 2. Increases in perfusion pressure were produced by mesenteric peri-arterial nerve stimulation at 10 Hz for 5 s at 2 min intervals and by bolus intra-arterial injections of the vasoconstrictors noradrenaline, angiotensin II and 5-hydroxytryptamine. 3. The intra-arterial infusion of platelet-activating factor (PAF) to produce a blood concentration of 3 X 10(-10) mol/L inhibited all responses to a similar extent. Intra-arterial prazosin (1-5 X 10(-9) mol/L), however, preferentially reduced responses to nerve stimulation and noradrenaline. 4. PAF at concentrations from 3 X 10(-11) to 10(-9) mol/L produced increasing inhibition of vasoconstrictor responses to nerve stimulation. The dose-response to PAF was shifted to the right by the concomitant intra-arterial infusion of the PAF antagonist SRI 63-441. 5. PAF at very low concentrations in vivo inhibits mesenteric vasoconstriction, produced by sympathetic nerve stimulation or various agonists, by a PAF-receptor mediated vasodilatation of the mesenteric vasculature.
authors.affiliation: Discipline of Clinical Pharmacology, University of Newcastle, New South Wales, Australia.
authors.forename: J F
authors.initials: JF
authors.lastname: Gerkens
mesh_terms: D000804:Angiotensin II / Q000494:pharmacology; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D004558:Electric Stimulation; D008297:Male; D009638:Norepinephrine / Q000494:pharmacology; D010972:Platelet Activating Factor / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D011224:Prazosin / Q000494:pharmacology; D011806:Quinolinium Compounds / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D012701:Serotonin / Q000494:pharmacology; D013152:Splanchnic Circulation / Q000187:drug effects*; D014661:Vasoconstriction / Q000187:drug effects*
chemical_list: D010972:Platelet Activating Factor; D011806:Quinolinium Compounds; C050531:SRI 63-441; D000804:Angiotensin II; D012701:Serotonin; D009638:Norepinephrine; D011224:Prazosin