Electroretinogram recordings of Drosophila.

Analysis of visual physiology in Drosophila photoreceptors has been central to understanding a number of important areas of modern biology, including the G-protein-coupled receptor cycle, phosphoinositide signaling, and calcium signaling. Analysis of photoreceptor performance and synaptic transmission are areas of neurobiology that have been studied using Drosophila photoreceptors as a model system. Electrophysiological analysis of responses to light is a powerful tool for characterizing and understanding visual transduction in Drosophila photoreceptors, and electroretinograms (ERGs) have long been used as a physiological assay in the Drosophila visual system. In these recordings, a microelectrode is placed on the eye and a reference electrode is placed elsewhere on the animal (typically in the thorax). Upon light stimulation, the voltage difference between these two electrodes is measured and displayed in real time. Because recordings are performed in live animals, all photoreceptor cells are intact and therefore surrounded by fluid containing endogenous concentrations of ions. Moreover, synaptic transmission between the photoreceptor and downstream laminar neurons can be detected.