<prompt> Histamine blocker in stomach act throughDecreasing cAMP in stomachIncreasing cAMP in stomachIncreasing IP3 in stomachDecreasing IP3 in stomach  <response>: Histamine H2 blockersinhibit the action of histamine ongastric H2 receptors thereby decreasing gastric acidity. They were considered a breakthrough in the treatment of peptic ulcer disease when first introduced. Refer kDT 6e 153 