title: Arylbenzazepines are potent modulators for the delayed rectifier K+ channel: a potential mechanism for their neuroprotective effects.
abstract: (+/-) SKF83959, like many other arylbenzazepines, elicits powerful neuroprotection in vitro and in vivo. The neuroprotective action of the compound was found to partially depend on its D(1)-like dopamine receptor agonistic activity. The precise mechanism for the (+/-) SKF83959-mediated neuroprotection remains elusive. We report here that (+/-) SKF83959 is a potent blocker for delayed rectifier K(+) channel. (+/-) SKF83959 inhibited the delayed rectifier K(+) current (I(K)) dose-dependently in rat hippocampal neurons. The IC(50) value for inhibition of I(K) was 41.9+/-2.3 microM (Hill coefficient = 1.81+/-0.13, n = 6), whereas that for inhibition of I(A) was 307.9+/-38.5 microM (Hill coefficient = 1.37+/-0.08, n = 6). Thus, (+/-) SKF83959 is 7.3-fold more potent in suppressing I(K) than I(A). Moreover, the inhibition of I(K) by (+/-) SKF83959 was voltage-dependent and not related to dopamine receptors. The rapidly onset of inhibition and recovery suggests that the inhibition resulted from a direct interaction of (+/-) SKF83959 with the K(+) channel. The intracellular application of (+/-) SKF83959 had no effects of on I(K), indicating that the compound most likely acts at the outer mouth of the pore of K(+) channel. We also tested the enantiomers of (+/-) SKF83959, R-(+) SKF83959 (MCL-201), and S-(-) SKF83959 (MCL-202), as well as SKF38393; all these compounds inhibited I(K). However, (+/-) SKF83959, at either 0.1 or 1 mM, exhibited the strongest inhibition on the currents among all tested drug. The present findings not only revealed a new potent blocker of I(K) , but also provided a novel mechanism for the neuroprotective action of arylbenzazepines such as (+/-) SKF83959.
authors.affiliation: State Key laboratory of Drug Research, Department of Pharmacology II, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China.
authors.forename: Xue-Qin
authors.initials: XQ
authors.lastname: Chen
authors.forename: Jing
authors.initials: J
authors.lastname: Zhang
authors.forename: John L
authors.initials: JL
authors.lastname: Neumeyer
authors.forename: Guo-Zhang
authors.initials: GZ
authors.lastname: Jin
authors.forename: Guo-Yuan
authors.initials: GY
authors.lastname: Hu
authors.forename: Ao
authors.initials: A
authors.lastname: Zhang
authors.forename: Xuechu
authors.initials: X
authors.lastname: Zhen
mesh_terms: D015647:2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-benzazepine / Q000494:pharmacology; D000818:Animals; D000831:Animals, Newborn; D001552:Benzazepines / Q000494:pharmacology*; D018491:Dopamine Agonists / Q000494:pharmacology; D006624:Hippocampus / Q000378:metabolism; D020128:Inhibitory Concentration 50; D009474:Neurons / Q000378:metabolism; D018696:Neuroprotective Agents / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D026902:Potassium Channel Blockers / Q000494:pharmacology; D015221:Potassium Channels / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D011954:Receptors, Dopamine / Q000378:metabolism
chemical_list: D001552:Benzazepines; D018491:Dopamine Agonists; D018696:Neuroprotective Agents; D026902:Potassium Channel Blockers; D015221:Potassium Channels; D011954:Receptors, Dopamine; D015647:2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-benzazepine