No evidence for differences between pre‐ and post‐junctional α2‐adrenoceptors

Abstract

1 We have examined the pre- and post-junctional effects of a series of α-adrenoceptor agonists and antagonists at α₂-adrenoceptors in the pithed rat preparation and the human isolated saphenous vein. 2 In the pithed rat, there was no difference in relative agonist and antagonist potencies between pre-and post-junctional α₂-adrenoceptors but the absolute potencies of antagonists differed: antagonists were more potent prejunctionally. 3 In the human saphenous vein, the α₂-adrenoceptor antagonist yohimbine had pre- and post-junctional actions over the same concentration range. 4 We have no evidence to suggest differences between pre- and post-junctional α₂-adrenoceptors: differences in absolute antagonist potencies in the pithed rat may be due to non-equilibrium conditions.