Synthesis of this compound is rate-limited by an enzyme that the W317X (“w-three-seventeen-x”) mutation truncates in Tourette’s syndrome. This is the main substrate of a copper-dependent enzyme that also metabolizes putrescine and cadaverine. Patients with intolerance for this compound take diamine oxidase supplements to break down this compound and avoid scombroid poisoning. The first blockbuster drug, cimetidine, selectively inhibits parietal cells’ receptors for this compound to treat (*) stomach ulcers. (-5[2])This compound is made by decarboxylating an imidazole-containing amino acid. The OTC (10[1])drugs loratadine and cetirizine block this compound’s activity after IgE causes its release from (10[1])mast cells, preventing a runny nose and itching. For 10 points, (10[1])seasonal allergies are treated by drugs (10[1])that target what inflammatory compound? ■END■ (10[2])