Activation of adenosine A receptor potentiates metabotropic glutamate receptor 1-mediated Ca mobilization in the rat hippocampal marginal zone.

Two subtypes of group I metabotropic glutamate receptors (mGluRs), mGluR1 and mGluR5, participate in the regulation of cell excitability and synaptic plasticity in the central nervous system. They couple to the G protein and release Ca from the intracellular stores. In the marginal zone of the neonatal hippocampus, Cajal-Retzius (CR) cells, which control radial migration of neurons, express the subtype mGluR1. The adenosine A1 receptor (AR) is also G-protein coupled and is extensively expressed in the central nervous system. The interactions among G-protein-coupled receptors have been predicted previously, however, there is insufficient evidence of functional interactions between naturally occurring receptors. In this study, potentiation of the mGluR1-mediated response by AR activation was demonstrated in hippocampal CR cells. Fluorescence imaging revealed that the application of AR agonists intensified mGluR1-induced elevation of intracellular Ca concentration ([Ca]). Activation of AR did not change [Ca]. The potentiated responses were independent of extracellular Ca and prevented by the G inhibitor. The potentiation of mGluR1-induced [Ca]. elevation was also enhanced by mGluR2/3 activation. These results suggest that mGluR1 and AR cooperatively influence postnatal hippocampal development by facilitating Ca mobilization in CR cells.