OBJECTIVE To explore the effects of
Caulis Sinomenii and sinomenine on the
conditioned place preference induced by morphine
in mice and its relation to cAMP level of the brain. METHOD Morphine was injected (9mg/kg, one time/day, sc) to mice for 5 days. The strong place preference was observed in mice. Mice were pretreated 45 min before each injection of morphine during 5 d training phase and treated only once 45 min before the testing phase at d 6 with
Caulis Sinomenii(5,10g/kg, ig)and sinomenine(60mg/kg, ig), respectively. Cyclic AMP content in the brain cortex of mice was measured by RIA.RESULTS The time of staying in morphine-paired compartment and the cAMP level in brain of mice in morphine group were significantly increased. After treatment with Caulis Sinomenii and sinomenine, the time of staying in morphine-paired compartment and the cAMP level in mice were significantly reduced.CONCLUSION Caulis Sinomenii and sinomenine could suppress the acquisition and expression of place preference induced by morphine. Their mechanism may be related to decrease of cAMP level in the brain.