title: The blockade of alpha 2-adrenoceptors by the PNMT inhibitaor SK&F 64139.
abstract: Three tetrahydroisoquinolines were tested for activity on central alpha 2-adrenoceptors by determining their ability to inhibit [3H]clonidine binding to rat cerebral cortical membrane homogenates. The compounds included the PNMT inhibitors SK&F 64139 (7,8-dichloro-1,2,3,4-tetrahydroisoquinoline) and SK&F 29661 (1,2,3,4-tetrahydroisoquinoline 7-sulfonamide) as well as SK&F 72223 (5,8-dimethoxy-1,2,3,4-tetrahydroisoquinoline) a structural analogue inactive as a PNMT inhibitor. SK&F 64139 and SK&F 72223 but not SK&F 29661 inhibited [3H]clonidine binding. Studies in the isolated guinea pig atrium confirmed that SK&F 64139 and SK&F 72223 are alpha 2-adrenoceptor antagonists.
mesh_terms: D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology*; D000818:Animals; D001665:Binding Sites; D002540:Cerebral Cortex / Q000378:metabolism; D003000:Clonidine / Q000378:metabolism; D066298:In Vitro Techniques; D007546:Isoquinolines / Q000494:pharmacology*; D010625:Phenylethanolamine N-Methyltransferase / Q000037:antagonists & inhibitors*; D051381:Rats; D011941:Receptors, Adrenergic / Q000187:drug effects*; D011942:Receptors, Adrenergic, alpha / Q000187:drug effects*; D044005:Tetrahydroisoquinolines
chemical_list: D000317:Adrenergic alpha-Antagonists; D007546:Isoquinolines; D011941:Receptors, Adrenergic; D011942:Receptors, Adrenergic, alpha; D044005:Tetrahydroisoquinolines; C012153:7,8-dichloro-1,2,3,4-tetrahydroisoquinoline; D010625:Phenylethanolamine N-Methyltransferase; D003000:Clonidine