Upon this study, we concluded that phosphorylation of ERK may contribute to intrathecal morphine-induced pruritus for following reasons: 1) We found that compared with the control group, mice treated with 0.5 μg intrathecal morphine exhibited elevated expression of pERK1/2 in the lumbar spinal cord dorsal horn at 5 min post-injection, which was in accordance with the peak of the scratching response. The gene discussed is MAPK1; the disease is Pruritus.