Localization of [3H]-2-deoxy glucose in single molluscan neurones

The glucose analogue 2-deoxyglucose (2-DG) can be used quantitatively to measure metabolic activity1 and is widely used qualitatively for mapping functional activity in the brain2–4. The resolution (meaning the full width at half maximum of the grain density distribution around a line source) of the technique using [14C]-2-DG and X-ray film is limited to about 100 µm5. Attempts have been made to improve the resolution using [3H]-2-DG (ref. 6) and cellular resolution has been achieved in the goldfish retina7 and with cultured mouse neurones8. An anatomical technique for mapping the metabolic activity of individual neurones would be useful for studying invertebrate central nervous systems, which are relatively simple and stereotyped compared to vertebrate brains. The [3H]-2-DG technique was applied to an invertebrate in a study of the Drosophila visual system9, though without cellular resolution. We present here modifications of the [3H]-2-DG technique to demonstrate localization of 2-DG in single neurones of Limax maximus, a gastropod mollusc, with a resolution of less than 1 µm.