The Medullary Dorsal Horn

Abstract

Data from this study demonstrate that the MDH is a site where morphine acts to produce facial scratching in monkeys by acting at opioid receptors. It is also likely that the MDH is a site where centrally administered opioids act in producing facial pruritus in humans. The effects of morphine on facial-scratching behavior were only modestly attenuated with chlorcyclizine, indicating a minor involvement of a histamine-dependent mechanism of action.