1. It is now established that α2-adrenoceptors can be present on vascular smooth muscle as targets for exogenous agonists, but some controversy exists as to whether these vascular α2-receptors may also be the target for neurally released noradrenaline.
2. In human saphenous vein we have found evidence that the α2-antagonist yohimbine in low concentrations (0.01 μmol/l) can significantly inhibit stimulation-evoked contractions, whereas the α1-antagonist prazosin is more than ten times less potent.
3. It is concluded that, at least in some tissues, neuro-effector transmission can be mediated by vascular α2-adrenoceptors.