title: Whole-cell recording of light-evoked photoreceptor responses in a slice preparation of the cuttlefish retina.
abstract: A new tissue slice preparation of the cuttlefish eye is described that permits patch-clamp recordings to be acquired from intact photoreceptors during stimulation of the retina with controlled light flashes. Whole-cell recordings using this preparation, from the retinas of very young Sepia officinalis demonstrated that the magnitude, latency, and kinetics of the flash-induced photocurrent are closely dependent on the magnitude of the flash intensity. Depolarizing steps to voltages more positive than -40 mV, from a membrane holding potential of -60 mV, induced a transient inward current followed by a larger, more sustained outward current in these early-stage photoreceptors. The latter current resembled the delayed rectifier (I(K)) already identified in many other nerve cells, including photoreceptors. This current was activated at -30 mV from a holding potential of -60 mV, had a sustained time course, and was blocked in a dose-dependent manner by tetraethylammonium chloride (TEA). The smaller, transient, inward current appeared at potentials more positive than -50 mV, reached peak amplitude at -30 mV and decreased with further depolarization. This current was characterized as the sodium current (I(Na)) on the basis that it was inactivated at holding potentials above -40 mV, was blocked by tetrodotoxin (TTX) and was insensitive to cobalt. Intracellular perfusion of the photoreceptors, via the patch pipette, demonstrated that U-73122 and heparin blocked the evoked photocurrent in a dose-dependent manner, suggesting the involvement of the phospholipase C (PLC) and inositol 1,4,5-triphosphate (InsP(3)), respectively, in the phototransduction cascade. Perfusion with cyclic GMP increased significantly the evoked photocurrent, while the inclusion of phorbol-12,13-dibutyrate reduced significantly the evoked photocurrent, supporting the involvement of cGMP and the diacylglycerol (DAG) pathways, respectively, in the cuttlefish transduction process.
authors.affiliation: School of Biological Sciences, University of Plymouth, UK. abdul.chrachi@plymouth.ac.uk
authors.forename: Abdesslam
authors.initials: A
authors.lastname: Chrachri
authors.forename: Lisa
authors.initials: L
authors.lastname: Nelson
authors.forename: Roddy
authors.initials: R
authors.lastname: Williamson
mesh_terms: D000779:Anesthetics, Local / Q000494:pharmacology; D000818:Animals; D000925:Anticoagulants / Q000494:pharmacology; D006152:Cyclic GMP / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004307:Dose-Response Relationship, Radiation; D004347:Drug Interactions; D004558:Electric Stimulation / Q000379:methods; D004963:Estrenes / Q000494:pharmacology; D006493:Heparin / Q000494:pharmacology; D066298:In Vitro Techniques; D008027:Light; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology / Q000528:radiation effects*; D008974:Mollusca; D018408:Patch-Clamp Techniques / Q000379:methods*; D015240:Phorbol 12,13-Dibutyrate / Q000494:pharmacology; D010726:Phosphodiesterase Inhibitors / Q000494:pharmacology; D010775:Photic Stimulation / Q000379:methods; D017956:Photoreceptor Cells, Invertebrate / Q000187:drug effects / Q000502:physiology / Q000528:radiation effects*; D026902:Potassium Channel Blockers / Q000494:pharmacology; D011760:Pyrrolidinones / Q000494:pharmacology; D011930:Reaction Time / Q000528:radiation effects; D026941:Sodium Channel Blockers / Q000494:pharmacology; D019789:Tetraethylammonium / Q000494:pharmacology; D013779:Tetrodotoxin / Q000494:pharmacology
chemical_list: D000779:Anesthetics, Local; D000925:Anticoagulants; D004963:Estrenes; D010726:Phosphodiesterase Inhibitors; D026902:Potassium Channel Blockers; D011760:Pyrrolidinones; D026941:Sodium Channel Blockers; C060229:1-(6-((3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl)-1H-pyrrole-2,5-dione; D015240:Phorbol 12,13-Dibutyrate; D013779:Tetrodotoxin; D019789:Tetraethylammonium; D006493:Heparin; D006152:Cyclic GMP