Smooth muscle of rabbit aorta contains ?1- but not ?2-Adrenoceptors

Abstract

We have investigated the residual contractile response to noradrenaline remaining after phenoxybenzamine (3×10⁻⁷ mol/l) in rabbit aorta, since it has been reported that phenoxybenzamine at low doses completely and irreversibly blocks α₁- but not α₂-adrenoceptors. The contraction elicited by noradrenaline slowly recovered with time after it had been almost abolished by phenoxybenzamine. This residual response was blocked by the α₁-selective antagonist prazosin (3×10⁻⁸ mol/l) but not by the α₂-selective antagonist rauwolscine (3×10⁻⁷ mol/l). The results confirm that the smooth muscle of rabbit aorta contains α₁- not α₂-adrenoceptors.