Identification of [3H]deoxyglucose-labelled interneurons in the fly from serial autoradiographs

Using the [3H]deoxyglucose technique we find in the third visual ganglion of the fly, Musca domestica, a number of neuronal profiles whose labelling strongly depends on the direction of visual movement. By reconstruction from serial autoradiographs of semithin sections the three-dimensional morphology of the labelled profiles, we demonstrate that cell bodies, neurites, axons and arborizations of two interneurons are labelled whose homologues in Calliphora have been identified as movement-sensitive centrifugal horizontal cells ('CH-cells'). A set of three other cells whose homologues in Calliphora show similar electrophysiological responses to horizontal movement ('HS-cells') exhibit very little label on either side. It is suggested that the relation between deoxyglucose mapping and physiological activity can be investigated at the cellular level by using this system of fly interneurons.