title: Modafinil inhibits K(Ca)3.1 currents and muscle contraction via a cAMP-dependent mechanism.
abstract: Modafinil has been used as a psychostimulant for the treatment of narcolepsy. However, its primary mechanism of action remains elusive. Therefore, we examined the effects of modafinil on K(Ca)3.1 channels and vascular smooth muscle contraction. K(Ca)3.1 currents and channel activity were measured using a voltage-clamp technique and inside-out patches in mouse embryonic fibroblast cell line, NIH-3T3 fibroblasts. Intracellular adenosine 3',5'-cyclic monophosphate (cAMP) concentration was measured, and the phosphorylation of K(Ca)3.1 channel protein was examined using western blotting in NIH-3T3 fibroblasts and/or primary cultured mouse aortic smooth muscle cells (SMCs). Muscle contractions were recorded from mouse aorta and rat pulmonary artery by using a myograph developed in-house. Modafinil was found to inhibit K(Ca)3.1 currents in a concentration-dependent manner, and the half-maximal inhibition (IC(50)) of modafinil for the current inhibition was 6.8 ± 0.7 nM. The protein kinase A (PKA) activator forskolin also inhibited K(Ca)3.1 currents. The inhibitory effects of modafinil and forskolin on K(Ca)3.1 currents were blocked by the PKA inhibitors PKI(14-22) or H-89. In addition, modafinil relaxed blood vessels (mouse aorta and rat pulmonary artery) in a concentration-dependent manner. Modafinil increased cAMP concentrations in NIH-3T3 fibroblasts or primary cultured mouse aortic SMCs and phosphorylated K(Ca)3.1 channel protein in NIH-3T3 fibroblasts. However, open probability and single-channel current amplitudes of K(Ca)3.1 channels were not changed by modafinil. From these results, we conclude that modafinil inhibits K(Ca)3.1 channels and vascular smooth muscle contraction by cAMP-dependent phosphorylation, suggesting that modafinil can be used as a cAMP-dependent K(Ca)3.1 channel blocker and vasodilator.
authors.affiliation: Department of Physiology, Medical School, Ewha Womans University, Seoul, South Korea.
authors.forename: Shinkyu
authors.initials: S
authors.lastname: Choi
authors.forename: Moon Young
authors.initials: MY
authors.lastname: Kim
authors.forename: Ka Young
authors.initials: KY
authors.lastname: Joo
authors.forename: Seonghee
authors.initials: S
authors.lastname: Park
authors.forename: Ji Aee
authors.initials: JA
authors.lastname: Kim
authors.forename: Jae-Chul
authors.initials: JC
authors.lastname: Jung
authors.forename: Seikwan
authors.initials: S
authors.lastname: Oh
authors.forename: Suk Hyo
authors.initials: SH
authors.lastname: Suh
mesh_terms: D000818:Animals; D001559:Benzhydryl Compounds / Q000494:pharmacology*; D002352:Carrier Proteins / Q000494:pharmacology; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation; D020536:Enzyme Activators / Q000494:pharmacology; D006801:Humans; D016285:Iloprost / Q000494:pharmacology; D051660:Intermediate-Conductance Calcium-Activated Potassium Channels / Q000037:antagonists & inhibitors* / Q000378:metabolism; D007546:Isoquinolines / Q000494:pharmacology; D008297:Male; D008564:Membrane Potentials; D051379:Mice; D000077408:Modafinil; D009131:Muscle, Smooth, Vascular / Q000187:drug effects* / Q000378:metabolism; D032389:Myocytes, Smooth Muscle / Q000187:drug effects* / Q000378:metabolism; D041681:NIH 3T3 Cells; D018408:Patch-Clamp Techniques; D010446:Peptide Fragments / Q000494:pharmacology; D010766:Phosphorylation; D026902:Potassium Channel Blockers / Q000494:pharmacology*; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D051381:Rats; D015290:Second Messenger Systems / Q000187:drug effects*; D013449:Sulfonamides / Q000494:pharmacology; D013997:Time Factors; D015854:Up-Regulation; D014661:Vasoconstriction / Q000187:drug effects*; D014665:Vasodilator Agents / Q000494:pharmacology*
chemical_list: D001559:Benzhydryl Compounds; D002352:Carrier Proteins; D020536:Enzyme Activators; D051660:Intermediate-Conductance Calcium-Activated Potassium Channels; D007546:Isoquinolines; C496925:Kcnn4 protein, mouse; C491575:Kcnn4 protein, rat; D010446:Peptide Fragments; D026902:Potassium Channel Blockers; D047428:Protein Kinase Inhibitors; D013449:Sulfonamides; D014665:Vasodilator Agents; C477818:myristoylated protein kinase A inhibitor amide 14-22; D005576:Colforsin; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; D016285:Iloprost; C063509:N-(2-(4-bromocinnamylamino)ethyl)-5-isoquinolinesulfonamide; D000077408:Modafinil