Postlesional transcriptional regulation of metabotropic glutamate receptors: implications for plasticity and excitotoxicity

Metabotropic glutamate receptors (mGluRs) seem to be involved both in neuro nal excitotoxicity evoked by pathological conditions such as ischemia, and in processes associated with neuronal plasticity and regulation of synaptic strength. Using semiquantitative reverse transcription-polymerase chain re action, we measured the messenger RNA levels of mGluR2-5, 24 h and 7 days a fter experimentally induced focal cortical infarcts in rat motor cortex. Th e mRNA level of mGluR3 was strikingly decreased ipsilaterally after 24 h. O n day 7, the expression of mGluR2 was down-regulated both ipsi- and contral aterally. Other receptors of this family showed either a slight or no regul ation at both time points. The early changes in the expression pattern of m GluRs might be primarily linked to excitotoxicity processes which occur imm ediately after an ischemic lesion in cortex, whereas the delayed changes mi ght represent one chain link in the cascade of compensatory mechanisms cont ributing to functional amelioration.