Functional characterisation of alpha(1)-adrenoceptors in denervated rat vas deferens

We investigated whether or not surgical denervation of the rat vas deferens changes the alpha(1)-adrenoceptor subtypes involved in the contractions to noradrenaline. Denervated vas deferens was approximately 22 times more sensitive to noradrenaline (pD(2)=7.35+/-0.04) than control vas (pD(2)=6.01+/-0.03). This difference in noradrenaline potency was eliminated when cocaine (6 microM) was added to control vas (pD(2)=7.22+/-0.04). The noradrenaline-induced contractions of control and denervated vas deferens were insensitive to the alpha(1B)/alpha(1D)-adrenoceptor alkylating agent chloroethylclonidine (100 microM, 45 min). The concentration-response curves to noradrenaline in control and denervated vas deferens were competitively antagonised by prazosin (pA(2) approximately equal to 9.6), WB-4101 (pA(2) approximately equal to 9.5), 5-methyl urapidil (pA(2) approximately equal to 8.4), phentolamine (pA(2) approximately equal to 8.7), yohimbine (pA(2) approximately equal to 6.9), BMY 7378 (pA(2) approximately equal to 6.9) and indoramin (pA(2) approximately equal to 8.7). After the treatment of control and denervated vas deferens with phenoxybenzamine, the partial agonist oxymetazoline antagonised competitively the concentration-response curves to noradrenaline showing pA(2) values approximately 7.4 in both groups. We conclude that noradrenaline-induced contractions in control and denervated rat vas deferens are mediated by alpha(1A)-adrenoceptors and that surgical denervation of the rat vas deferens is not able to change the alpha(1)-adrenoceptor subtypes involved in the contractions to noradrenaline.