A fluorometric procedure to image release of the neurotransmitter glut
amate from living retinal slices is described. Patterns of endogenous
glutamate afflux were imaged with a cooled CCD camera in goldfish reti
nal slices as NADH fluorescence produced by a cycling glutamate dehydr
ogenase (GDH). Basal and potassium evoked glutamate effluxes were stro
ngly localized to the outer and inner plexiform layers, supporting the
model that photoreceptors and bipolar cells release glutamate as thei
r prime fast neurotransmitter. (C) 1998 Elsevier Science Ltd. All righ
ts reserved.