Assessment of Ca ²⁺ dynamics in IALVs from control and Ip3r1ismKO mice using GCaMP6f. Ca²⁺ was recorded over 20–30 s at 20 fps in pressurized and contracting IALVs from MyH11CreER^T2-GCaMp6f mice or Ip3r1ismKO-GCaMP6f mice (Videos 3 and 4). (A and B) Representative maximum projections of the lymphatic muscle Ca²⁺ signal and outline of individual lymphatic muscle cells for analysis. Scale bars are 50 μm. (C and D) Plot profiles and their respective space-time maps of Ca²⁺ over time (x-axis) from the outlined cells in A and B for IALVs from MyH11CreER^T2-GCaMp6f mice or Ip3r1ismKO-GCaMP6f mice, respectively. (E and G) Analysis of the Ca²⁺ flash associated with contraction for (E) frequency, (F) amplitude, and (G) duration as assessed by full width at half-maximum. (H) Lymphatic muscle cells in IALVs from Ip3r1ismKO mice largely lack diastolic Ca²⁺ transients (pink and orange arrow heads in C, green arrowheads in D) and the number of analyzed cells that displayed diastolic Ca²⁺ transients (H) in either IALVs from MyH11CreER^T2-GCaMp6f mice or Ip3r1ismKO-GCaMP6f mice were tabulated. n = 8 MyH11CreER^T2-GCaMp6f and n = 9 Ip3r1ismKO-GCaMp6f IALVs with mean and SEM shown and stated explicitly beneath the graphs.