Cajal-Retzius cells in early postnatal mouse cortex selectively express functional metabotropic glutamate receptors

Glutamate receptors have been linked to the regulation of several developme ntal events in the CNS. By using cortical slices of early postnatal mice, w e show that in layer I cells, glutamate produces intracellular calcium ([Ca 2+](i)) elevations mediated by ionotropic and metabotropic glutamate recept ors (mGluRs). The contribution of mGluRs to these responses was demonstrate d by application of tACPD, an agonist to groups I and II mGluRs, which evok ed [Ca2+](i) increases that could be reversibly blocked by MCPG, an antagon ist to groups I and II mGluRs. In the absence of extracellular Ca2+, repeti tive applications of tACPD or quisqualate, an agonist to group I mGluRs, el icited decreasing [Ca2+](i) responses that were restored by refilling a tha psigargin-sensitive Ca2+ store. The use of specific group I mGluR agonists CHPG and DHPG indicated that the functional mGluR in layer I was of the mGl uR1 subtype. Subtype specific antibodies confirmed the presence of mGlur1 a lpha, but not mGluR5, in Cajal-Retzius (Reelin-immunoreactive) neurons.