Evaluation of Peripheral Itch Mechanisms Following Injection of Morphine

During the 1st session, each of the middle forearms of the subject will be divided into two squared areas (4x4 cm) located 3 cm apart. Two areas will be treated with an intradermal injection of morphine (0.05 ml, 0.1 mg/ml), and two areas with an intradermal injection of isotonic saline.