Pharmacological differentiation of postsynaptic alpha adrenoceptors in the dog saphenous vein.
The dog saphenous vein has postsynaptic subpopulations of both alpha-1 and alpha-2 adrenoceptors which are easily demonstrable using selective agonists and antagonists. Specific alpha-1 (methoxamine and SK&F 89748) or mixed alpha-1, alpha-2 (l-norepinephrine and M7) agonists as well as the specific alpha-2 agonist, BHT 920, cause concentration-related contraction of this tissue. However, maximum contractions produced by alpha-2 activation are significantly less than maximum contractions produced by alpha-1 or combined alpha-1, alpha-2 adrenoceptor activation. SK&F 89748-induced contractions are competitively inhibited by prazosin (pA2 = 7.74) and rauwolscine (pA2 = 6.63); BHT 920-induced contractions are unaffected by prazosin but inhibited by rauwolscine (pA2 = 8.93). Contractile responses to l-norepinephrine are inhibited by prazosin, rauwolscine or phenoxybenzamine in a manner that suggests that norepinephrine interacts with two subtypes of alpha adrenoceptors in this tissue. These data indicate that the dog saphenous vein strip is a suitable in vitro preparation for study of drug action at both postsynaptic adrenoceptors inasmuch as either subpopulation of alpha adrenoceptor can be studied independently using specific agonists or antagonists.
D000818:Animals; D001381:Azepines / Q000494:pharmacology; D004285:Dogs; D005260:Female; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000378:metabolism*; D009284:Naphthols / Q000494:pharmacology; D009638:Norepinephrine / Q000494:pharmacology; D010643:Phenoxybenzamine / Q000494:pharmacology; D011224:Prazosin / Q000494:pharmacology; D011942:Receptors, Adrenergic, alpha / Q000378:metabolism*; D012501:Saphenous Vein / Q000378:metabolism; D013764:Tetrahydronaphthalenes / Q000494:pharmacology; D015016:Yohimbine / Q000494:pharmacology
D001381:Azepines; D009284:Naphthols; D011942:Receptors, Adrenergic, alpha; D013764:Tetrahydronaphthalenes; D010643:Phenoxybenzamine; D015016:Yohimbine; C009957:5,6-dihydroxy-2-dimethylaminotetralin; C024763:talipexole; C039140:SK&F 89748; D009638:Norepinephrine; D011224:Prazosin