title: Postjunctional alpha 2-adrenoceptors in blood vessels of human nasal mucosa.
abstract: Human nasal mucosa has various types of blood vessels and is a good tissue for demonstrating receptors for many vasoactive substances, including alpha-adrenoceptors. In contrast to the large contractile response induced by alpha 1-agonists, our studies have shown that alpha 2-agonists produce a small maximal contraction. This alpha 2-induced response was easily blocked by alpha 1-antagonists, indicating that it is evoked, at least partially, by the stimulation of alpha 1-adrenoceptors. Noradrenaline (NA)-induced contractions could not be abolished by either alpha 1- or alpha 2-antagonists alone, but were almost completely blocked by the combination of both antagonists. This suggests the presence of postjunctional alpha 2-adrenoceptors. The low-maximal responsiveness to alpha 2-agonists and calcium independency of NA-induced contractions were distinct from our former results obtained on canine nasal specimens.
mesh_terms: D000316:Adrenergic alpha-Agonists / Q000008:administration & dosage / Q000145:classification / Q000493:pharmacokinetics; D000317:Adrenergic alpha-Antagonists / Q000493:pharmacokinetics; D002118:Calcium / Q000493:pharmacokinetics; D006801:Humans; D066298:In Vitro Techniques; D009119:Muscle Contraction / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000032:analysis*; D009297:Nasal Mucosa / Q000032:analysis / Q000098:blood supply*; D009638:Norepinephrine / Q000008:administration & dosage / Q000493:pharmacokinetics; D011941:Receptors, Adrenergic / Q000032:analysis* / Q000187:drug effects; D013569:Synapses; D013997:Time Factors; D014661:Vasoconstriction / Q000187:drug effects
chemical_list: D000316:Adrenergic alpha-Agonists; D000317:Adrenergic alpha-Antagonists; D011941:Receptors, Adrenergic; D002118:Calcium; D009638:Norepinephrine