Trafficking of receptors to and from the cell surface is a powerful mechanism for regulating neuronal excitability. To date, the majority of studies concerning glutamate receptor trafficking have been performed in neuronal cultures in which surface expression can be readily assayed by immunofluorescence techniques. Results from such studies have had important implications in the field of synaptic plasticity. However, cultured neurons are, by necessity, prepared from very young animals. Moreover, although an enhancement of excitatory neurotransmission can be induced in such systems, classic long-term potentiation (LTP) can be produced only in acute slices or in vivo. To study trafficking in adult tissues, we have adapted two biochemical techniques, proteolysis and cross-linking. These techniques help define surface-expressed and intracellular pools of native receptors in acute hippocampal slices.