GPIb-dependent FeCl₃-induced stable occlusion of the carotid artery requires Tp (thromboxane receptor). (A) The tracings are representative of blood flow in FeCl₃-treated exposed carotid arteries of wild-type and Tp^-/- mice. Blood flow was monitored for 45 minutes, including a 3-minute treatment starting at zero time with a strip of filter paper soaked in 10% Fe Cl₃. The arrow indicates the time of removal of the FeCl₃-containing strip of filter paper. (B) Box-plot graphs represent time of first occlusion of carotid arteries (blood flow less than 0.2 mL/min) from 6 WT mice and 6 Tp^-/- mice. The results show that the median time required for the first thrombotic occlusion in 6 WT mice was 4 minutes, with a range of 2 to 6 minutes; the median time required for the first thrombotic occlusion in the Tp^-/- arteries was 22.5 minutes, with a range of 13 to 45 minutes. Arterial blood flow was occluded in all the wild-type arteries at the end of the monitoring period. On the contrary, all of the treated Tp^-/- arteries were patent at the end of the monitoring period. No occlusion occurred in the treated carotid artery of one Tp^-/- mouse. These results demonstrate that Tp is required for GPIb-dependent stable thrombus formation in vivo. Bars represent extreme values for times of first occlusion.