Fig. 6. Cross talk between IP3R and RyR.A, MeCh-evoked global [Ca2+]i rises were mediated by IP3Rs in OPs. Ca2+ rises were measured in fluo-3-loaded OPs using wide-angle microscopy at a collection speed of 1 frame/sec. Responders were cells that showed a fluorescence rise >10% over the prestimulus baseline level. A1, At lower concentrations of agonist, agents that inhibit PLC or block IP3Rs abolished evoked Ca2+ responses. Cells were pretreated with U73122 (10 μm) or XeC (20 μm) for 20 min or perfused with 2-APB for 5 min before testing with MeCh. A2, Cells responding to 3 μm MeCh were inhibited by IP3R antagonists. The plot shows that peak amplitude of global Ca2+responses was significantly inhibited by XeC and 2-APB. B, C, Elementary events were modulated by agents that block IP3Rs or RyRs. Elementary events evoked by 30 nm MeCh or 2 mm DMPX were recorded in fluo-4-loaded OP processes using line scan confocal microscopy.B1, Ryanodine (10 μm) enhanced and XeC reduced the amplitude of MeCh (30 nm)-evoked events.B2, Ryanodine also enhanced the width of MeCh-evoked events. C, DMPX events were modulated by pretreatment with MeCh (3 μm). C1, Three minutes after pulsing with MeCh, DMPX events showed a higher amplitude (p = 0.0238; n = 24).C2, Five minutes after MeCh, DMPX event width was increased (p = 0.0005; n= 17). C3, A diagram of the three MeCh prepulse protocols. Cells were treated with MeCh (M) for 15 sec, then washed for 1, 3, or 5 min (open bar) before testing with DMPX (stippled bar). C4, Ca2+ stores were not depleted by the MeCh pulse, as shown in this representative trace from a wide-angle microscopy experiment (n = 440). MeCh applied for 15 sec (black bars) at 3, 5, and 1 min intervals evoked repeatable amplitude Ca2+responses.