A comparison was made of contractile responses to α-adrenoceptor agonists in the rat aorta and in the rat isolated perfused femoral artery. Dose-response curves were constructed to noradrenaline (α1/α2), methoxamine (α1-selective) and B-HT 920 (α2-selective). Methoxamine behaved as a full agonist in both tissues as compared with noradrenaline, while B-HT 920 was only a partial agonist in the aorta and produced small responses in the femoral artery preparation which were not dose-dependent. pA2 or -log KB values were calculated for prazosin and idazoxan against noradrenaline and methoxamine. Similar -log KB values for prazosin against were obtained in both tissues, while idazoxan was approximately ten times more potent in the femoral artery preparation than in the aorta. These results suggest that the aorta contains a single population of α1-adrenoceptors, while the perfused femoral artery preparation contains predominantly α1-adrenoceptors but also a small population of α2-adrenoceptors.
- Femoral artery (perfused)
- α-Adrenoceptors (postjunctional)