Research Article Cone-Like Rectification Properties of cGMP-Gated Channels in Transmutated Retinal Photoreceptors of Nocturnal Geckoes Vittorio Vellani 1 and Chiara Giacomoni 2 1 Dipartimento di Scienze Biomediche Metabolismo e Neuroscienze, Universit` a di Modena e Reggio Emilia, via Campi 287, 41125 Modena, Italy 2 Dipartimento di Economia Scienze e Diritto, c/o Corso di Laurea in Ingegneria, Universit` a della Repubblica di San Marino, Salita alla Rocca 44, 47890 Citt` a di San Marino, San Marino Correspondence should be addressed to Vittorio Vellani; vvellani@unimore.it Received 31 July 2014; Revised 22 October 2014; Accepted 30 October 2014; Published 23 November 2014 Academic Editor: Heping Xu Copyright © 2014 V. Vellani and C. Giacomoni. his is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Photoreceptors of nocturnal geckoes are scotopic, with rod-shaped outer segments, and sensitivities to light similar to the one of retinal rods from other species of lower vertebrates. However, these cells are not rods, but they originated from cones of ancestral diurnal geckoes with pure-cone retinas, ater being forced to adapt to a nocturnal behavior. Several interesting adaptations of these rod-like cones have been studied to date; molecular biology and functional studies conirmed that several proteins of the phototransductive cascade display structural and functional properties that indicate their origin from cones rather than from rods. In this paper, we investigate, with whole cell voltage clamp in the photoreceptor detached outer segment preparation, the voltage rectiication properties of cGMP-gated channels in three species, Gekko gecko, Tarentola mauritanica, and Hemidactylus frenatus. We show that the current-voltage properties in the physiological voltage range are reminiscent of the ones of cGMP-gated channels from cones rather than from rods of other cold-blooded vertebrates. he origin and the relevance of the mechanisms investigated are discussed. 1. Introduction he nature and the molecular origin of the diferences between rod and cone function represent a highly relevant question in the study of phototransduction in vertebrates. Modern nocturnal geckos possess retinas with only rod- shaped photoreceptors; however, phylogenetic analysis of the Gekkonidae family suggests that both today’s nocturnal and diurnal geckos evolved from a common ancestor with cone- only retinas. herefore, photoreceptors of nocturnal geckos, despite the rod-like shape, ultrastructure, and function [1–3], are actually cones evolutionarily adapted to fulill the role of rods and allow scotopic vision. his hypothesis was originally proposed by Walls and it is known as “transmutation theory” [4, 5]. Because of their intermediate physiological properties between rods and cones, photoreceptors from nocturnal geckos represent an outstanding model for the investigation of the physiological and molecular diferences between these cell types, which may lead to general quantitative and quali- tative cues on the mechanisms of phototransduction. Qualitatively, exposure to light in both rods and cones causes a decrease in intracellular cGMP concentration ([cGMP] i ), which in turn causes the closure of the cGMP- gated channel expressed in the plasma membrane of outer segment, the light-sensitive portion of vertebrate photorecep- tors, and eventually produces hyperpolarization. he cGMP- gated channel is diferent in rods and cones [6], and the two diferent types of channels behave diferently in several respects [7–9]. Previous investigation on gecko photorecep- tors focused attention largely on the molecular structure of the visual pigments [10, 11] and more recently on the structure of other proteins of the phototransductive cascade [12]. No previous comparative study investigated the functional properties of the cGMP-gated channels in nocturnal gecko photoreceptors. In this study, we analyze the rectiication Hindawi Publishing Corporation e Scientific World Journal Volume 2014, Article ID 942510, 6 pages http://dx.doi.org/10.1155/2014/942510