Non-correspondence of [3H]GABA uptake and GAD localization in goldfish amacrine cells

Ultrastructural analysis of the inner synaptic layer of goldfish retina, using a double-label technique, showed that [3H]GABA uptake and glutamic acid decarboxylase (GAD)-immunoreactivity (IR) occurred in different neuronal processes in most cases. Many [3H]GABA-accumulating processes were found surrounding GAD-IR processes, though not necessarily in a postsynaptic relationship. Co-localization of [3H]GABA uptake and GAD-IR occurred only when one GAD-IR process was juxtaposed to another GAD-IR process. This study suggests that [3H]GABA uptake may be a poor marker for GABA releasing neurons.