Characterization of alpha-adrenoceptors in the preprostatic urethra of sexually immature male lambs

European Journal of Pharmacology
A García-PascualA García-Sacristán


Strips of preprostatic urethra from immature male lambs (3-4 months old) were used to study alpha-adrenoceptor-mediated contractions in vitro. The rank order of potency of the agonists was noradrenaline = phenylephrine greater than adrenaline. B-HT 920 was ineffective and clonidine behaved as a weak partial agonist. The rank order of efficacy was found to be noradrenaline greater than phenylephrine greater than adrenaline. Prazosin (10(-9)-10(-6) M) and rauwolscine (10(-6)-10(-4) M) antagonized noradrenaline-induced contractions. The pA2 values were 7.89 and 5.38 for prazosin and rauwolscine, respectively. Phenoxybenzamine reduced the maximal response to noradrenaline and shifted the concentration-response curve to the right. The dissociation constant (KA) of noradrenaline was calculated to be 4.05 +/- 0.21 x 10(-6) M and the occupancy-response plot for noradrenaline showed a linear relationship. It is concluded that alpha-adrenergic contraction of the preprostatic urethra from immature lambs are mediated by alpha 1-adrenoceptors. It is also suggested that the lack of a receptor reserve may affect the degree of urethral constriction and could be related to hormonal status.


Feb 11, 1986·European Journal of Pharmacology·F YablonskyJ P Dausse
Feb 1, 1984·British Journal of Pharmacology·K E AnderssonC Sjögren
Mar 1, 1959·British Journal of Pharmacology and Chemotherapy·O ARUNLAKSHANA, H O SCHILD

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