Department of Biological Sciences, University of Iowa Iowa City, Iowa 52242 U.S.A,
It is important to establish the links between the genes and behavior such that the biochemical defects and corresponding behavioral changes can be understood in neural terms. However, neurons in the Drosophila central nervous system are thought to be too small in size for serious physiological investigations. An attempt was initiated two decades ago to study the cell types and their physiological properties of neurons in the first optic lobe, lamina, in the brain. Using intracellular microelectrode techniques, electrical potentials in response to light stimuli were recorded and the cells were stained by injection of a fluorescent dye via the same micropipette. The structure of the lamina and the surrounding tissue were also studied by scanning electron microscopy. The results indicated that different cell types, identifiable by intracellular staining, produce either depolarizing or hyperpolarizing potentials of a variety of kinetic properties. By applying currents to shift membrane potential, the reversal potentials of the light responses could be determined. The large number of response types characterized by distinct kinetic properties and reversal potentials observed reflects a rich variety of synaptic processes in the visual pathway. The data provide the necessary groundwork for further analyses potentially a large collection of Drosophila mutants defective in the development or physiology in the visual system. This work also serves to demonstrate that neurons in the Drosophila brain is in principle and reality accessible to cellular physiological analysis. I thank Dr. William Pak, in whose lab a portion of the work was initiated and accomplished, for support and encouragement