... of muscarinic acetylcholinereceptor -induced Ins(1,4,5)P3 increases in PC12h cells, we utilized anIns(1,4,5)P3 imaging system based on fluorescence resonance energy trans-fer and using green ... (CFP–PHD and YFP–PHD, respectively) werecoexpressed in PC12h cells, and their interaction wasanalyzed by measuring changes in fluorescence inten-sity. Increases in cellular calcium and Ins(1,4,5)P3were induced ... onIns(1,4,5)P3production was further investigated by separately analyzing receptor- and calcium -induced Ins(1,4,5)P3 increases. The level of receptor -induced Ins(1,4,5)P3was about half that induced by the combi-nation...