Receptor-operated Ca influx and transmitter release

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In PC12 cells expressing・1A-adrenoceptor, methoxamine evoked intracellular Ca release which was followed by Ca influx. The Ca influx was mediated via receptor-operated Ca channel, and was enhanced by overexpression of snapin but was reduced by knockdown of TRPC. The change in intracellular Ca ion was greatly associated with the release of endogenous dopamine, suggesting a direct relationship between GqPCR-mediated intracellular Ca increase and transmitter release in culture cells. However, in rat striatum slices preloaded with ^3H-dopamine GqPCR-mediated dopamine release was not observed. M1-muscarinic acetylcholine receptor occurs at both plasma membrane and intracellular sites in rat cerebral cortex and N1E-115 neuroblastoma cells, coupled to two distinct signaling systems.