Glutamate Receptors Are Selectively Targeted to Postsynaptic Sites in Neurons

The objective of the present study was to determine if a neuron that expresses multiple glutamate receptors targets the same receptors to all glutamatergic postsynaptic populations, or if the receptors are differentially targeted to specific postsynaptic populations. As a model for this study, we chose the fusiform cell of the dorsal cochlear nucleus. This neuron expresses multiple glutamate receptors and receives two distinct glutamatergic inputs: parallel fibers synapse on apical dendrites, and auditory nerve fibers synapse on basal dendrites. Pre- and postembedding immunocytochemistry were combined with retrograde tracing to identify the receptors expressed on postsynaptic membranes of parallel fiber and auditory nerve synapses. Most receptors were found at both populations of synapses, but the AMPA receptor subunit, GluR4, and the metabotropic receptor, mGluR1 alpha, were found only at the auditory nerve synapse. These results demonstrate that glutamate receptors are targeted to specific postsynaptic populations of glutamatergic synapses.