Differential labelling of retinal neurones by ³H-2-deoxyglucose

Abstract

THE delineation of structural and functional interconnections in the vertebrate retina has long been a central problem in vision research. The Golgi technique^1,2, combined with ultrastructural studies^3,4 and post-recording injection of intracellular stains^5,6, has revealed the morphological and physiological properties of many of the individual cell types of the retina. Recently, light and electron microscope autoradiography with putative neurotransmitters has tentatively identified certain retinal neurones with specific transmitters^7,8. However, very few techniques exist which can reveal the interconnections of a ‘pathway’ of retinal neurones in a functionally dependent manner. Radioactive 2-deoxyglucose (2-DG) is commonly used as a tracer in the central nervous system, where biochemical and autoradiographic studies have shown it to be a good indicator of local functional activity^9–11. Transport and phosphorylation of 2-DG are identical to those of glucose, but no further metabolism beyond 2-DG-6-PO₄ occurs¹². Most published studies using 2-DG as a tracer have used the ¹⁴C-labelled form and frozen thick-sectioned tissue, a combination in which the resolution of morphological structure is unacceptable for studying neuronal connections in the retina. In the studies reported here, we have used tritium-labelled 2-DG in combination with plastic embedding to produce stimulus-dependent labelling at the cellular level in the isolated goldfish retina; our results suggest that these modifications of the ‘2-deoxyglucose technique’ are useful for studying the physiology and functional connections of retinal neurones.