Selective clustering of glutamate and gamma-aminobutyric acid receptors opposite terminals releasing the corresponding neurotransmitters.

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Abstract
Several immunocytochemical and physiological studies have demonstrated a concentration of neurotransmitter receptors at postsynaptic sites on neurons, but an overall picture of receptor distribution has not emerged. In particular, it has not been clear whether receptor clusters are selectively localized opposite terminals that release the corresponding neurotransmitter. By using antibodies against the excitatory glutamate receptor subunit GluR1 and the inhibitory type A gamma-aminobutyric acid (GABA) receptor beta 2/3 subunits, we show that these different receptor types cluster at distinct postsynaptic sites on cultured rat hippocampal neurons. The GABAA receptor beta 2/3 subunits clustered on cell bodies and dendritic shafts opposite GABAergic terminals, whereas GluR1 clustered mainly on dendritic spines and was associated with glutamatergic synapses. Chronic blockade of evoked transmitter release did not block receptor clustering at postsynaptic sites. These results suggest that complex mechanisms involving nerve terminal-specific signals are required to allow different postsynaptic receptor types to cluster opposite only appropriate presynaptic terminals.