SELECTIVE CLUSTERING OF GLUTAMATE AND GAMMA-AMINOBUTYRIC-ACID RECEPTORS OPPOSITE TERMINALS RELEASING THE CORRESPONDING NEUROTRANSMITTERS

Several immunocytochemical and physiological studies have demonstrated a concentration of neurotransmitter receptors at postsynaptic sites o n neurons, but an overall picture of receptor distribution has not eme rged. In particular, it has not been clear whether receptor clusters a re selectively localized opposite terminals that release the correspon ding neurotransmitter, By using antibodies against the excitatory glut amate receptor subunit GluR1 and the inhibitory type A gamma-aminobuty ric acid (GABA) receptor beta 2/3 subunits, we show that these differe nt receptor types cluster at distinct postsynaptic sites on cultured r at hippocampal neurons. The GABAA receptor beta 2/3 subunits clustered on cell bodies and dendritic shafts opposite GABAergic terminals, whe reas GluR1 clustered mainly on dendritic spines and was associated wit h glutamatergic synapses. Chronic blockade of evoked transmitter relea se did not block receptor clustering at postsynaptic sites. These resu lts suggest that complex mechanisms involving nerve terminal-specific signals are required to allow different postsynaptic receptor types to cluster opposite only appropriate presynaptic terminals.