Effect of a New Antihypertensive Drug, Urapidil, On Pre- and Postsynaptic α-Adrenoceptors in Guinea-Pig and Rat Vas Deferens

Urapidil, phentolamine (both 10−8−10−5M), and clonidine (10−6−10−5M) competitively antagonized the effect of noradrenaline on postsynaptic α-adrenoceptors in organ bath-suspended rat vas deferens, yielding pA2 values of 7.02, 7.64 and 5.81, respectively.