Preparation of dissociated ommatidia from Drosophila

Adult Drosophila have a compound eye composed of approximately 750 repeating units, called ommatidia, packed together to form the retina. Each ommatidium is a precise arrangement of 19 cells: eight photoreceptors (primary sensory neurons) and 11 accessory cells. 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. This protocol describes the isolation of dissociated ommatidia for use in voltage-clamp recordings of currents from photoreceptors, allowing detailed analysis of ion channels such as the transient receptor potential and potassium channels in photoreceptors. Mechanical dissociation of ommatidia is typically performed in flies that are <4 h post-eclosion. In animals older than this, the ommatidia become progressively more firmly attached to each other and cannot be dissociated mechanically without causing substantial damage to the constituent photoreceptors. Like the rest of the fly, the eye is surrounded by a cuticle. Thus, before the dissociation process, the eye is dissected from the rest of the head and the retina is scooped out of the cuticular covering.