title: Block by apomorphine of acetylcholine receptor channels expressed in Xenopus oocytes.
abstract: Effects of apomorphine and other compounds related to dopamine receptors on nicotinic acetylcholine receptor channels were investigated by expressing functional channels in Xenopus oocytes. When channels were expressed with a combination of alpha 3 and beta 4 subunits, acetylcholine activated an inward current, and apomorphine suppressed the current in a concentration-dependent manner with an IC50 value of about 3 microM. SKF38393 (R(+)-1-phenyl-2,3,4,5-tetrahydro-(1H)-3-benzazepine-7,8-diol; dopamine D1 receptor agonist; 3 and 30 microM), quinpirole (dopamine D2 receptor agonist; 30 microM), SCH23390 (R(+)-7-chloro-8-hydroxy-3-methyl-1-phenyl-2,3,4,5-tetrahydro-1H-3-benza zepine; dopamine D1 receptor antagonist; 10 microM) or sulpiride (dopamine D2 receptor antagonist; 10 microM) also inhibited the acetylcholine-activated current whereas dopamine (100 microM) was ineffective. The inhibition by apomorphine of the acetylcholine-activated current was also apparent when alpha 3 subunit was combined with beta 2 subunit instead of beta 4 subunit, or beta 4 subunit was combined with alpha 2 or alpha 4 subunit instead of alpha 3 subunit to express channels. The results suggest that apomorphine blocks acetylcholine receptor channels through a binding site that is similar to, but cannot be included in dopamine receptors. The binding site may not be present in a single specific subunit.
authors.affiliation: Division of Pharmacology, National Institute of Health Sciences, Tokyo, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Nakazawa
authors.forename: T
authors.initials: T
authors.lastname: Akiyama
authors.forename: K
authors.initials: K
authors.lastname: Inoue
mesh_terms: D015647:2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-benzazepine / Q000378:metabolism / Q000494:pharmacology; D000818:Animals; D001058:Apomorphine / Q000494:pharmacology*; D001667:Binding, Competitive; D004298:Dopamine / Q000378:metabolism / Q000494:pharmacology; D018491:Dopamine Agonists / Q000378:metabolism / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D004873:Ergolines / Q000378:metabolism / Q000494:pharmacology; D018733:Nicotinic Antagonists; D009865:Oocytes; D018408:Patch-Clamp Techniques; D019257:Quinpirole; D051381:Rats; D011978:Receptors, Nicotinic / Q000187:drug effects / Q000378:metabolism; D013469:Sulpiride / Q000378:metabolism / Q000494:pharmacology; D014158:Transcription, Genetic / Q000235:genetics; D014982:Xenopus laevis
chemical_list: D018491:Dopamine Agonists; D004873:Ergolines; D018733:Nicotinic Antagonists; D011978:Receptors, Nicotinic; D019257:Quinpirole; D015647:2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-benzazepine; D013469:Sulpiride; D001058:Apomorphine; D004298:Dopamine