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 (-5[1])and avoid scombroid poisoning. The first blockbuster drug, cimetidine, selectively inhibits parietal cells’ receptors for this compound to treat (*) stomach ulcers. This compound is made by decarboxylating an imidazole-containing amino acid. The OTC drugs loratadine and cetirizine block this compound’s activity after IgE causes its release from mast cells, preventing a runny (10[1])nose and itching. For 10 points, seasonal allergies are treated by drugs that target what inflammatory compound? ■END■ (10[1])