Objective:To explore the possible role of ? endorp hi n in effect of melatonin on morphine withdrawal symptoms in rats.Method:Acute model of morphine dependent rat was estalished by gradually increasing the dose of morphine through subcutaneous injections.CSF(cerebrospinal fluid)w a s got by push-pull perfusion and intracerebroventricular injection(icv)in a fixe d tuber.Concentration of ? endorphin in CSF was determined by radioimmunoassa y (RIA).Results:(1)The symptoms of natural morphine withdrawal were r e lieved significantly by icv ? Endorphin with a dose dependent manner.(2)The s y mptoms of natural morphine withdrawal were also relieved by ip melatonin.(3)The CSF ? endorphin level was significantly lower in morphine dependent rats than normal control,but that was higher in natural morphine withdrawal rats.That was also much more increased by ip melatonin in the withdrawal rats than in morphine dependent rats or normal control.Conclusion:The withdrawal symptom s could be relieved by icv ? endorphin or by ip melatonin in morphine dependetn rats.The mechanism may be partly due to the elevation of endogenous ? endorp hin level in brain of rats in withdrawal

AIM: To investigate the change of adrenocorticotropic hormone (ACTH) cells and thyroid- stimulating hormone(wn) cells of pars distalls of pituitary gland of morphine dependent dependent rats and its restoration after withdrawal. METHODS: Morphine dependent model of male rats was made by subcutaneous injection of mor- phine and the adstinent model was made after withdrawal. Changes of ACTH cells and TSH cells of pars distails of pituitary gland were detected by immunohistochemistoy survey and image analysis. RESULTS: The intensity of positive staining and the numerical density of ACTH and TSH immunoreactive cells were weakened (P＜ 0.01), after withdrawal from morphine for a short time the changes would exist continuously. CONCLUSION: Morphine may give rise to disorder of endocrine of pituitary gland of male rats, which may incompletely restore after withdrawal for a short time.