Evidence for functional alpha-adrenoceptors in rabbit basilar arteries.

The contractile response of rabbit basilar arteries to 1-norepinephrine was studied both in the absence and in the presence of prazosin (10 nM and 1 microM). Prazosin produced a parallel shift to the right of the norepinephrine, but not the histamine, dose-response curves indicating the presence of prazosin-sensitive alpha-adrenoceptors in this vessel. The alpha-adrenoceptor-mediated contractile responses to norepinephrine in rabbit basilar arteries were much more sensitive to the deleterious effects of storage (for 18 h at 4 degrees C) than those to histamine. It is suggested that the low number of alpha-adrenoceptors in the rabbit basilar artery combined with their low sensitivity to alpha-adrenoceptor agonists, and detrimental effects associated with tissue storage may explain some inconsistent reports in the literature regarding the presence of functional alpha-adrenoceptors in rabbit basilar arteries, particularly ligand binding studies.