Isolation of light-induced response of the central retinula cells from the electroretinogram ofDrosophila

An intense blue light stimulus induces a prolonged depolarizing after-potential (PDA) in the peripheral retinula cells, but not in the central retinula cells, of theDrosophila ommatidia, providing the fly has been dark or red adapted and the screening pigments have been genetically removed from the compound eye. Thus, the PDA saturates only the peripheral retinula cells, allowing one to isolate and study extracellularly the summed receptor potentials (SR) of the central retinula cells (Fig. 1). The following lines of evidence support these ideas