[Effects of scopolamine on serotonin in the spinal cord and atria of morphine-dependent rats].

The effects of scopolamine on serotonin (5-HT) in the spinal cord and atria of morphine-dependent rats were studied. Levels of 5-HT and its metabolite, 5-hydroxyindolactic acid (5-HIAA) in the spinal cord and atria were analyzed by HPLC-ECD method. The results showed that contents of 5-HT, 5-HIAA in the spinal cord of morphine-dependent rats were statistically higher than those of controls (P < 0.01, n = 6), and that scopolamine inhibited morphine's effect by decreasing 5-HT, 5-HIAA in the spinal cord. After acute abstinence (1d), the contents of 5-HT in the spinal cord in natural withdrawal group were decreased, but increased in scopolamine group. After chronic abstinence (6d), the contents of 5-HT in the spinal cords in the two groups were all increased to above normal level. The results also showed that scopolamine did not affect the increasing of 5-HT in atria induced by morphine. The data support a role of muscarinic receptor on changes of 5-HT metabolism in the spinal cord in morphine-dependent rats.