Abstract
The effect of a range of prostanoids on human and rabbit basilar arteries precontracted in vitro in the presence of the thromboxane receptor-blocking drug AH23848B was investigated. On the rabbit basilar artery and in the presence of AH23848B the thromboxane A2 mimetic U-46619 produced further concentration-related contractions of the tissue. All other prostaglandins (except ICI81008 and PGF 2a which had no effect) produced concentration-related relaxations with the rank order of relaxant potency being PGE2 > Iloprost > PGI2 = PGE1 = 16,16–dimethyl PGE 2 = PGD2. On the human basilar artery PGI2 and iloprost produced concentration-related relaxations with iloprost being more potent than PGI2. At high concentrations both these compounds produced reduced relaxant responses. All other prostanoids (except ICI81008 and PGD2 which had no effect) contracted the tissue, the rank order of contractile potency being 16, 16–dimethyl PGE2 > PGE2 > PGF2a = PGE2 > U46619 > ICI81008 and PGD2. It is concluded that the human basilar artery possesses two contractile prostanoid receptors, a TP receptor and one which may be of the EP-type in addition to a prostanoid receptor mediating relaxation which may be of the IP-type. The prostanoid receptor(s) mediating relaxation of the rabbit in vitro basilar artery is difficult to determine. The relevance of the observations to cerebrovascular disorders such as migraine and vasospasm is discussed.
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