title: Vasodilator effect of terbutaline: in vivo evidence for the existence of beta 2-adrenoceptors in the microcirculation of rats, hamsters, and guinea pigs.
abstract: The characteristics of beta 2-adrenoceptors were studied in vivo in the microcirculation of cremaster muscle and mesoappendix in rats, cheek pouch in hamsters, and mesentery in guinea pigs, using a video-microscope technique. Terbutaline (beta 2-selective agonist) caused vasodilatation in all four microcirculation preparations studied, whereas butoxamine (beta 2-selective antagonist) competitively inhibited the terbutaline-induced vasodilatation. The in vivo pA2 values of butoxamine inhibition of terbutaline vasodilator effect were estimated from Schild plots. The pA2 values (6.22-6.31) were statistically identical in all four microcirculations studied and similar to in vitro values reported in other tissues. In contrast, tazolol and prenalterol (both beta 1-selective agonists) did not produce any vasodilatation in the microcirculations studied. These results supported the existence of beta 2-adrenoceptors involved in vasodilatation in the microcirculation.
mesh_terms: D000818:Animals; D002078:Butoxamine / Q000494:pharmacology; D006224:Cricetinae; D004305:Dose-Response Relationship, Drug; D006168:Guinea Pigs; D008297:Male; D008647:Mesocricetus; D008833:Microcirculation / Q000032:analysis* / Q000187:drug effects; D011217:Practolol / Q000031:analogs & derivatives / Q000494:pharmacology; D011294:Prenalterol; D011412:Propanolamines / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D011943:Receptors, Adrenergic, beta / Q000032:analysis*; D013726:Terbutaline / Q000494:pharmacology*; D014665:Vasodilator Agents / Q000494:pharmacology*
chemical_list: D011412:Propanolamines; D011943:Receptors, Adrenergic, beta; D014665:Vasodilator Agents; D002078:Butoxamine; C002268:tazolol; D011294:Prenalterol; D013726:Terbutaline; D011217:Practolol