Metabotropic glutamate receptor 5 (mGluR5) is expressed by neurons in zones of active neurogenesis and is involved in the development of neural stem cells in vivo and in vitro.We examined the expression of mGluR5 in the cortex and hippocampus of rats during various prenatal and postnatal periods using immunohistochemistry.During prenatal development,mGluR5 was primarily localized to neuronal somas in the forebrain.During early postnatal periods,the receptor was mainly present on somas in the cortex.mGluR5 immunostaining was visible in apical dendrites and in the neuropil of neurons and persisted throughout postnatal development.During this period,pyramidal neurons were strongly labeled for the receptor.In the hippocampal CA1 region,mGluR5 immunoreactivity was more intense in the stratum oriens,stratum radiatum,and lacunosum moleculare at P0,P5 and P10 relative to P60.mGluR5 expression increased significantly in the molecular layer and decreased significantly in the granule cell layer of the dentate gyrus at P5,P10 and P60 in comparison with P0.Furthermore,some mGluR5-positive cells were also bromodeoxyuridine-or NeuroD-positive in the dentate gyrus at P14.These results demonstrate that mGluR5 has a differential expression pattern in the cortex and hippocampus during early growth,suggesting a role for this receptor in the control of domain specific brain developmental events. Metabotropic glutamate receptor 5 (mGluR5) is expressed by neurons in zones of active neurogenesis and is involved in the development of neural stem cells in vivo and in vitro. We examined the expression of mGluR5 in the cortex and hippocampus of rats during various prenatal and postnatal periods using immunohistochemistry. Early prenatal development, mGluR5 was primarily localized to neuronal somas in the forebrain. Early teatal stages, the receptor was mainly present on somas in the cortex. mGluR5 immunostaining was visible in apical dendrites and in the neuropil of neurons and persisted throughout postnatal development. During this period, pyramidal neurons were strongly labeled for the receptor. In the hippocampal CA1 region, mGluR5 immunoreactivity was more intense in the stratum oriens, stratum radiatum, and lacunosum moleculare at P0, P5 and P10 relative to P60.mGluR5 expression increased significantly in the molecular layer and decreased significantly in the granule cell layer o f the dentate gyrus at P5, P10 and P60 in comparison with P0.Furthermore, some mGluR5-positive cells were also bromodeoxyuridine-or NeuroD-positive in the dentate gyrus at P14. These results demonstrate that mGluR5 has a differential expression pattern in the cortex and hippocampus during early growth, suggesting a role for this receptor in the control of domain specific brain developmental events.