Modulation of Ca2+ signals by phosphatidylinositol-linked novel D1 dopamine receptor in hippocampal neurons

Recent evidence indicates the existence of a putative novel phosphatidylinositol-linked D1 dopamine receptor in brain that mediates phosphatidylinositol hydrolysis via activation of phospholipase C beta. The present work was designed to characterize the Ca2+ signals regulated by this phosphatidylinositol-linked D-1 dopamine receptor in primary cultures of hippocampal neurons. The results indicated that stimulation of phosphatidylinositol-linked D1 dopamine receptor by its newly identified selective agonist SKF83959 induced a long-lasting increase in basal [Ca2+](i) in a time- and dose-dependent manner. Stimulation was observable at 0.1 mu M and reached the maximal effect at 30 mu M. The [Ca2+](i) increase induced by 1 mu M SKF83959 reached a plateau in 5 +/- 2.13 min, an average 96 +/- 5.6% increase over control. The sustained elevation of [Ca2+](i) was due to both intracellular calcium release and calcium influx. The initial component of Ca2+ increase through release from intracellular stores was necessary for triggering the late component of Ca2+ rise through influx. We further demonstrated that activation of phospholipase C beta/inositol triphosphate was responsible for SKF83959-induced Ca2+ release from intracellular stores. Moreover, inhibition of voltage-operated calcium channel or NMDA receptor-gated calcium channel strongly attenuated SKF83959-induced Ca2+ influx, indicating that both voltage-operated calcium channel and NMDA receptor contribute to phosphatidylinositol-linked D-1 receptor regulation of [Ca2+](i).