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The rat tail artery has been used for the study of vasoconstriction mediated by α_1A-adrenoceptors (ARs). However, rings from proximal segments of the tail artery (within the initial 4 cm, PRTA) were at least 3-fold more sensitive to methoxamine and phenylephrine (n = 6–12; p < 0.05) than rings from distal parts (between the sixth and 10th cm, DRTA). Interestingly, the imidazolines N-[5-(4,5-dihydro-1H-imidazol-2-yl)-2-hydroxy-5,6,7,8-tetrahydronaphthalen-1-yl]methanesulfonamide hydrobromide (A-61603) and oxymetazoline, which activate selectively α_1A-ARs, were equipotent in PRTA and DRTA (n = 4–12), whereas buspirone, which activates selectively α_1D-AR, was ≈70-fold more potent in PRTA than in DRTA (n = 8; p < 0.05). The selective α_1D-AR antagonist 8-[2-[4-(methoxyphenyl)-1-piperazinyl]ethyl]-8-azaspiro[4.5]decane-7,9-dione dihydrochloride (BMY-7378) was ≈70-fold more potent against the …