Coexpression patterns of mGLuR mRNAs in rat retinal ganglion cells: A single-cell RT-PCR study

PURPOSE. Eight different subunits of metabotropic glutamate receptors (mGlu Rs) are known to date. mGluRs have been linked to an extensive list of neur omodulatory: effects, depending on which intracellular or membrane-bound ef fector system is activated. Activation of mGluRs can influence neuronal act ivity and can result in changes of intracellular Ca2+ homeostasis-that is, changes in factors that are known to be crucial for cellular differentiatio n and cell death. Because mGluRs are known in modulating both intracellular and intercellular activities, this study was designed to determine which t ypes of mGluRs are coexpressed in a neuron and whether distinct coexpressio n patterns can be found that reflect the different physiological requiremen ts of a neuron at different stages of development and to learn whether neur onal injury results in adaptive changes of mGluR expression. METHODS. Juvenile and adult rat retinal ganglion cells (RGCs) and adult RGC s after axotomy were analyzed for their gene expression pattern of mGluRs b y single-cell reverse transcription-polymerase chain reaction (RT-PCR). RESULTS, Adult RGCs predominantly expressed one or two different mGluR mRNA s, whereas juvenile RGCs coexpressed two and more. mGluR3, -5, and -7 mRNAs were found more frequently in juvenile than in adult RGCs. mGluR6 was dete cted in juvenile RGCs in low abundance but never in adult RGCs. However, mG luR6 was expressed in adult RGCs after axotomy. mGluR1 and -7 were also fou nd more frequently in axotomized RGCs than in the adult control group. CONCLUSIONS. All types of mGluR mRNAs are expressed in RGCs, This is in con trast with previous in situ hybridization and immunohistochemical studies i n which expression of mGluR3, -5, and -6 was not reported. The expression o f some mGluR mRNAs seems to be developmental, :although nc, distinct copatt erns were found.