Multiplicity of glutamate receptor subunits in single striatal neurons: an RNA amplification study

The RNA amplification technique was used to examine the pattern of coexpression of mRNAs encoding 16 subtypes/subunits of the glutamate receptor (GluR) in acutely dissociated neurons from adult rat striata. THe signal intensity for each mRNA varied within single neurons, but the general pattern of low versus high expression signals was similar among neurons, except for the GluR4 subunit of the (+/-)-alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor. The mRNAs for GluR1-3 subunits of the AMPA receptor were present in all cells, with the signal intensity of GluR1 mRNAs usually the lowest. The kainate receptor subunit mRNAs (GluR5-7) were present in most neurons, and the signal intensity for GluR6 mRNA was the highest. The signals for N-methyl-D-aspartate (NMDA)R1 and NMDAR2B mRNAs were high in most neurons; however, NMDAR2A and NMDAR2C mRNAs gave low or undetectable signals. For mRNAs encoding metabotropic GluRs (mGluRs), signals for mGluR1, mGluR2, and mGluR3 mRNAs were low or undetectable, whereas mGluR4 and mGluR5 mRNA signals were high in most neurons. In most cases (12 of 16 mRNAs), the results agreed with data from in situ hybridization experiments in which individual mRNAs were examined. All neurons expressed subtypes/subunits mRNAs for all four types of GluRs; however, there were differences in the relative intensity of the mRNA signals detected in individual cells, suggesting that these receptors could exist in various combinations within individual neurons and thus confer synapse-specific function for information processing in the striatum.