alpha 1- and alpha 2-vascular adrenoceptors in the dog.
Prazosin inhibited contractions of isolated electrically stimulated dog pulmonary artery preincubated with (-)-7-3H-norepinephrine, but had no effect on 3H-overflow, whereas yohimbine enhanced both responses. In pithed dogs the cumulative doses of yohimbine required for 50% inhibition of the pressor effects of clonidine, phenylephrine and norepinephrine were 23, 188 and 35 micrograms/kg i.v., and those for prazosin were 9, 1.5 and 5 micrograms/kg i.v., respectively. The agonists could be ranked in pairs depending on the extent to which the antagonists discriminated members of the pair: clonidine-phenylephrine > phenylephrine-norepinephrine > clonidine-norepinephrine. The results suggest that pressor effects in dogs are mediated by both alpha 1- and alpha 2-vascular (i.e. postsynaptic) adrenoceptors.
D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D004285:Dogs; D004347:Drug Interactions; D005260:Female; D066298:In Vitro Techniques; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects*; D009131:Muscle, Smooth, Vascular / Q000187:drug effects*; D011224:Prazosin / Q000494:pharmacology; D011651:Pulmonary Artery / Q000187:drug effects; D011941:Receptors, Adrenergic / Q000187:drug effects*; D011942:Receptors, Adrenergic, alpha / Q000187:drug effects*; D015016:Yohimbine / Q000494:pharmacology
D011941:Receptors, Adrenergic; D011942:Receptors, Adrenergic, alpha; D015016:Yohimbine; D011224:Prazosin