Imaging of glutamate release from the goldfish retinal slice.

A fluorometric procedure to image release of the neurotransmitter glutamate from living retinal slices is described. Patterns of endogenous glutamate efflux were imaged with a cooled CCD camera in goldfish retinal slices as NADH fluorescence produced by a cycling glutamate dehydrogenase (GDH). Basal and potassium evoked glutamate effluxes were strongly localized to the outer and inner plexiform layers, supporting the model that photoreceptors and bipolar cells release glutamate as their prime fast neurotransmitter.