Activation of adenosine A 1 receptor potentiates metabotropic glutamate receptor 1-mediated Ca 2+ 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 _q/11 protein and release Ca ²⁺ 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 (A ₁ R) 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 A ₁ R activation was demonstrated in hippocampal CR cells. Fluorescence imaging revealed that the application of A ₁ R agonists intensified mGluR1-induced elevation of intracellular Ca ²⁺ concentration ([Ca ²⁺ ] _i ). Activation of A ₁ R did not change [Ca ²⁺ ] _i . The potentiated responses were independent of extracellular Ca ²⁺ and prevented by the G _i inhibitor. The potentiation of mGluR1-induced [Ca ²⁺ ] _i . elevation was also enhanced by mGluR2/3 activation. These results suggest that mGluR1 and A ₁ R cooperatively influence postnatal hippocampal development by facilitating Ca ²⁺ mobilization in CR cells.
Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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