Figure 1.

Muscarinic activation with ACh and the IP₃ signaling pathway in beta cells and acinar cells. (a) Acinar and beta cells express muscarinic receptors (M_XRs), activation of which results in IP₃ and DAG production. IP₃ specifically binds to IP₃R on the ER and triggers Ca²⁺ mobilization, leading to an oscillatory rise in [Ca²⁺]_c. Additionally, RYR receptors can be activated. L-type VDCCs play a role in Ca²⁺ refilling of the ER. (b) Color-coded time courses for beta (light brown) and acinar cells (blue) simultaneously stimulated with 8 mM glucose in combination with a physiological (50 nM, top traces) or a supraphysiological (25 µM, bottom traces) ACh concentration. The activation onsets after the cells were stimulated for the acinar cells (red) and the beta cells (green) are indicated with the vertical dashed lines. Legend: M_xR = muscarinic receptor, ACh = acetylcholine, DAG = diacylglycerol, IP₃ = 1,4,5-inositol trisphosphate, IP₃R = inositol (1,4,5) trisphosphate receptor, RYR = ryanodine receptors. Created with [40].