Distribution of functional glutamate and GABA receptors on hippocampal pyramidal cells and interneurons

The distribution of functional neurotransmitter receptors is an important d eterminant of neuronal information processing. To map the location of funct ional glutamate and GABA receptors on individual hippocampal neurons, we ph otolyzed "caged" glutamate and GABA while measuring the electrical currents resulting from activation of these receptors. Responses to uncaged neurotr ansmitters were spatially nonuniform and varied according to the type of re ceptor and type of neuron. Every region of CA1 pyramidal cells responded to glutamate and GABA, but glutamate and GABA receptors increased in density along the length of their distal dendrites. Similar gradients of glutamate receptors were found in stratum radiatum interneurons, while GABA responses were detectable only in the perisomatic region of these interneurons. Thes e regional variations in receptor distribution indicate the selective targe ting of receptors on central neurons and may reflect a mechanism for local regulation of synaptic efficacy.