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

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Recent evidence indicates the existence of a putative novel phosphatidylinositol-linked D1 dopamine receptor in brain that mediates phosphatidylinositol hydrolysis via activation of phospholipase Cβ. The present work was designed to characterize the Ca2+ signals regulated by this phosphatidylinositol-linked D1 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 μM and reached the maximal effect at 30 μM. The [Ca2+]i increase induced by 1 μM 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 Cβ/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 D1 receptor regulation of [Ca2+]i.

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