A Pharmacological Analysis of the α-Adrenoceptor Antagonism by Prazosin in Arteries and Veins

Schulz, John C.; Westfall, David P.

doi:10.1159/000158375

Cited by 4 publications

(1 citation statement)

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“…The value ofprazosin and the selective a-adrenoceptor agonists The absence of functional postjunctional a2-adrenoceptors in Group 1 blood vessels, as suggested by the high corynanthine/rauwolscine ratio, is supported by the high potency and competitive antagonism produced by prazosin against NA contractions in the thoractic aorta (Honda et al, 1985), ear artery (Purdy et al, 1980;Hieble et al, 1982) and the left renal vein (Schultz & Westfall, 1982). While the pA2 values are less than those obtained for prazosin at a,-adrenoceptors from the rat (see: Figure 5), they are within the expected range for al-adrenoceptor antagonist activity in the rabbit.…”

Section: Discussionmentioning

confidence: 99%

An examination of the postjunctional α‐adrenoceptor subtypes for (−)‐noradrenaline in several isolated blood vessels from the rabbit

Daly¹,

McGrath²,

Wilson³

1988

British J Pharmacology

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1 Postjunctional a-adrenoceptors in several isolated blood vessels from the rabbit have been characterized on the basis of the relative potency of the agonists noradrenaline (NA, non-selective), phenylephrine (a,-selective) and UK-14304 (a2-selective), and the potency of antagonists rauwolscine (x2-selective) and corynanthine (a,-selective) against contractions elicited by NA. In addition, the potency of prazosin against NA was also assessed in the venous preparations. 2 The thoracic aorta, ear artery and left renal vein appear to possess ax-adrenoceptors since the agonist potency order was NA > phenylephrine > UK-14304, while corynanthine was 3-10 fold more potent than rauwolscine. 3 The ear vein appears to possess a2-adrenoceptors. The rank order of agonist potency was UK-14304 > NA > phenylephrine and all three agonists elicited responses of similar magnitude. Furthermore, rauwolscine was 30 fold more potent than corynanthine while prazosin failed to produce a concentration-dependent inhibition. 4 The saphenous vein and the plantaris vein appear to possess a mixture of both subtypes since the rank order of agonist potency was UK-14304 > NA > phenylephrine, while responses elicited by UK-14304 were smaller than those to the other agonists. However, although rauwolscine was 20 to 100 fold more potent than corynanthine in both preparations, suggestive of predominantly a2-adrenoceptors, prazosin was either potent (saphenous vein) or relatively inactive (plantaris vein). 5 The characteristics of postjunctional al-and 02-adrenoceptors on isolated blood vessels from the rabbit are discussed in relation to the value of both the agonists, particularly NA, and the antagonists used in this study.

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Section: Discussionmentioning

confidence: 99%