Intracellular calcium mobilization in response to simultaneous stimulation of the G_i and G_z signaling. Fura-loaded, aspirinated, washed human platelets were stimulated as noted under stirring conditions at 37°C. Where noted, the antagonist 200 μM MRS2179 was added 1 minute prior to the addition of other agonists. Arrows indicate addition of agonist. Tracings are representative of results obtained from 3 different donors.