Identification of [ 3H]P1075 binding sites and P1075-activated K + currents in ovine choroid plexus cells

• Published in: European journal of pharmacology 1998-03, Vol.345 (1), p.97-101
• Main Authors: Dickinson, Kenneth E.J, Baska, Rose Ann, Cohen, Robert B, Bryson, Catherine C, Smith, Mark A, Schroeder, Kirk, Lodge, Nicholas J
• Format: Article
• Language: English
• Subjects: Adenosine Triphosphate - metabolism; Animals; Binding Sites - drug effects; Biological and medical sciences; Cells, Cultured; Cerebral circulation. Blood-brain barrier. Choroid plexus. Cerebrospinal fluid. Circumventricular organ. Meninges; Choroid plexus; Choroid Plexus - drug effects; Choroid Plexus - metabolism; Electrophysiology; Fundamental and applied biological sciences. Psychology; Glyburide; Guanidines - pharmacology; K + channel opener; K ATP channel; Kinetics; Levcromakalim; Membrane potential; Membrane Potentials - drug effects; P1075; Patch-Clamp Techniques; Potassium Channel Blockers; Potassium Channels - agonists; Potassium Channels - metabolism; Pyridines - pharmacology; Sheep; Vasodilator Agents - pharmacology; Vertebrates: nervous system and sense organs
• ISSN: 0014-2999; 1879-0712
• DOI: 10.1016/S0014-2999(97)01617-8

This study examined the pharmacological characteristics of binding sites for the potent K + channel opener [ 3H]P1075, as well as the functional effects of P1075 on ionic currents and membrane potential, in ovine choroid plexus (OCP) cells. [ 3H]P1075 bound to OCP cells with a K d of 26±4 nM and a B max of 10 400±480 sites/cell. Labelled sites were stereoselective and inhibited by potassium channel openers with a rank order of potency: P1075>BMS-182264, ((4-[[9cyanoimino)[(1,2,2-trimethylpropyl)amino]-methyl]amino]benzonitrile)>pinacidil≫nicorandil>diazoxide. The K ATP channel antagonist glyburide inhibited [ 3H]P1075 binding with a K i of 2 μM. The presence of K ATP channels on OCP cells was examined by patch clamp and fluorescent (membrane-potential sensitive dye) techniques. In some cells, P1075 activated an outward potassium current which was blocked by glyburide. P1075 produced a glyburide-sensitive, concentration-dependent, hyperpolarization of OCP cells. Levcromakalim hyperpolarized more strongly than its 3 R,4 S enantiomer, BRL 38226 ((3 R- trans)-3,4-dihydro-3-hydroxy-2,2-dimethyl-4-(2-oxo-1-pyrrolidinyl)-2 H-1-benzopyran-6-carbonitrile) indicating a stereoselective interaction. These data indicate that epithelial OCP cells contain glyburide-sensitive K ATP channels.