Alpha 1-adrenoceptor subtype involved in the positive inotropic response to phenylephrine in rat atria.
Phenylephrine produced positive inotropic responses in isolated rat right and left atria. The responses were competitively inhibited by alpha 1-adrenoceptor antagonists (prazosin, WB4101 and HV723) with relatively low affinities (pA2 values close to 8.0). Chloroethylclonidine had no significant effect on the responses to phenylephrine. These results suggest that the positive inotropic response to phenylephrine in rat atria is mediated through alpha 1-adrenoceptors which cannot be defined by the alpha 1A, alpha 1B subclassification.
Noguchi
H
H
Second Department of Surgery, Fukui Medical School, Japan.
Muraoka
R
R
Kigoshi
S
S
Muramatsu
I
I
D000097:Acetonitriles / Q000494:pharmacology; D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology*; D000818:Animals; D003000:Clonidine / Q000031:analogs & derivatives / Q000494:pharmacology; D004146:Dioxanes / Q000494:pharmacology; D006325:Heart Atria / Q000187:drug effects / Q000378:metabolism; D066298:In Vitro Techniques; D008297:Male; D009200:Myocardial Contraction / Q000187:drug effects*; D010656:Phenylephrine / Q000494:pharmacology*; D011224:Prazosin / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D011942:Receptors, Adrenergic, alpha / Q000187:drug effects / Q000502:physiology*
D000097:Acetonitriles; D000317:Adrenergic alpha-Antagonists; D004146:Dioxanes; D011942:Receptors, Adrenergic, alpha; C058562:HV 723; D010656:Phenylephrine; C051731:chlorethylclonidine; C010654:(2-(2',6'-dimethoxy)phenoxyethylamino)methylbenzo-1,4-dioxane; D003000:Clonidine; D011224:Prazosin