Differential Expression Profile of Class I and Class III Metabotropic Glutamate Receptors during Postnatal Development of Rat Hippocampus

The expression profile of neurotransmitter receptors changes significantly during brain development. In particular, the postnatal regulation of glutamate receptor expression may play a critical role in synaptogenesis, formation of neuronal circuitries and neuronal vulnerability. In this study, we have analyzed the mRNA expression profile of excitatory class I metabotropic glutamate receptors (mGluR) mGluR1 and mGluR5 as well as the inhibitory class III receptors mGluR4 and mGluR7 during postnatal hippocampal development in the rat using a competitive RT-PCR assay. A transient upregulation was observed for mGluR1 with a peak expression at postnatal day 30. The expression for mGluR4 and mGluR5 continuously declined during postnatal maturation (postnatal days 4–90). In contrast, the decline of mGluR7 expression was less substantial in this period. This divergent pattern of mGluR gene expression during postnatal development of the hippocampus may correspond to neuronal pattern formation and plasticity, but may also provide a molecular basis for altered seizure susceptibility and neuronal vulnerability in the developing rat hippocampus.