A crucial role for cAMP and protein kinase A in D1 dopamine receptor regulated intracellular calcium transients

D1-like dopamine receptors stimulate Ca²⁺ transients in neurons but the effector coupling and signaling mechanisms underlying these responses have not been elucidated. Here we investigated potential mechanisms using both HEK 293 cells that stably express D1 receptors (D1HEK293) and hippocampal neurons in culture. In D1HEK293 cells, the full D1 receptor agonist SKF 81297 evoked a robust dose-dependent increase in Ca²⁺_i following 'priming' of endogenous G_q/11-coupled muscarinic or purinergic receptors. The effect of SKF81297 could be mimicked by forskolin or 8-Br-cAMP. Further, cholera toxin and the cAMP-dependent protein kinase (PKA) inhibitors, KT5720 and H89, as well as thapsigargin abrogated the D1 receptor evoked Ca ²⁺ transients. Removal of the priming agonist and treatment with the phospholipase C inhibitor U73122 also blocked the SKF81297-evoked responses. D1R agonist did not stimulate IP₃ production, but pretreatment of cells with the D1R agonist potentiated G_q-linked receptor agonist mobilization of intracellular Ca²⁺ stores. In neurons, SKF81297 and SKF83959, a partial D1 receptor agonist, promoted Ca²⁺ oscillations in response to G_q/11-coupled metabotropic glutamate receptor (mGluR) stimulation. The effects of both D1R agonists on the mGluR-evoked Ca ²⁺ responses were PKA dependent. Altogether the data suggest that dopamine D1R activation and ensuing cAMP production dynamically regulates the efficiency and timing of IP₃-mediated intracellular Ca²⁺ store mobilization.