there is now a large body of evidence for the existence of postjunctional alpha-adrenoreceptors mediating the contraction of vascular smooth muscles that are resistant to blockade by the alpha 1-adrenoreceptor antagonist prazosin , but are blocked by alpha 2-antagonists and can be activated by selective alpha 2-agonists but not by selective alpha 1-agonists .
C0034784
alpha-adrenoreceptors
C0001638
alpha 1-adrenoreceptor