Effect of AJN on TH density by immunohistochemical staining. Representative staining pictures and effect of AJN on TH density by immunohistochemical staining. TH density in the striatum is decreased in the morphine group. Both AJN pre- and post-treatment effectively attenuates this decrease. NS: control group; Mor: morphine group. Data are expressed as the means ± SD (*p < 0.05, **p < 0.01, vs. morphine group; n = 5; Student’s t-test).