Role of myosin IIA and Rho kinase in regulating thrombus stability in vivo. Vascular injury was induced in the mesenteric postcapillary venules of anesthetized C57/Bl6 mice by needle puncture, and thrombus development recorded as described in “Intravital microscopy.” In the indicated experiments, the effects of blebbistatin, an inactive enantiomer of blebbistatin (control), vehicle (DMSO), or H1152 on thrombus stability was assessed following intermittent injections (denoted by ▀), with concentrations and volumes as described in “Intravital microscopy.” (A) The relative change in surface area of a given thrombus over time was determined off-line, and expressed relative to the initial surface area of the thrombus prior to injection. These results depict data taken from 1 of 4 independent experiments, with representative images from one such experiment depicted in panel B. The percentage decrease in thrombus surface area following injection was quantified as described in “Intravital microscopy,” and expressed as a percentage (%) of the original thrombus. These results represent the mean plus or minus SEM (n = 4), where *** indicates P < .001.