HETEROGENEITY OF VASCULAR SMOOTH MUSCLE α‐ADRENOCEPTORS IN CANINE BLOOD VESSELS

1. For the past decade, using radioligand binding, contractility and immunohistochemical techniques, we have been characterizing vascular smooth muscle (VSM) adrenoceptors in four functionally different canine blood vessels, namely the dog aorta (DAO), dog mesenteric artery (DMA), dog mesenteric vein (DMV) and dog saphenous vein (DSV). 2. This communication briefly reviews our findings (with a special emphasis on alpha-adrenoceptor subtypes), which showed that none of the four canine vessels showed the same complement of alpha-adrenoceptor subtypes. 3. All four vessels elicited alpha 1-adrenoceptor contractile responses (antagonized by prazosin), but alpha 2-adrenoceptor responses (sensitive to rauwolscine), were found only in DMV and DSV. 4. Pharmacological characterization using alpha 1-adrenoceptor subtype-selective antagonists showed that DAO contains mainly alpha 1B-adrenoceptors (some alpha 1D-adrenoceptors) and DMA has primarily alpha 1A/1L-adrenoceptors, alpha 1-Adrenoceptors in DMV are primarily of the alpha 1D subtype, but either a new or unusual alpha 1-adrenoceptor subtype was revealed in the DSV.