Effects of melatonin on learning and memory activity and number of hippocampal CA1 neurons in mice of morphine withdraw

Objective To observe the effects of melatonin(MT)on learning and memory activity and number of hippocampal CA1 neurons in mice induced by morphine withdraw and explore its mechanism.Method A physical dependent model of morphine in mice was established by subcutaneous injection of morphine.At the same time,MT was administered by intragastric perfusion with three different dose(2.5,5 and10mg·kg -1 ,respectively).Naloxone(5mg·kg -1 ) was administered intra-peritoneally to intensify addiction.The withdrawal syndrome was observed and the learning and memory was tested by the electric mare method.After behavioral test,the animals were sacrificed,the total brain tissues were removed,fixed,sliced,and then morphological observation were performed.Results The infacacy of learning and memory in three groups with different dose of MT were significantly higher than that of morphine withdrawal group( P 0.05, P 0.01and P 0.001,respectively),and a significan relation exiseted between MT dosage and effects in these dosage.The number of cells in hippocampal CA1 neurous in three different dose of MT groups were higher significantly than that of morphine withdraw group ( P 0.05, P 0.01and P 0.001 respectively).Conclusion MT plays a very important role in improving impaired learning and memory capacity induced by morphine withdraw in mice. The effect may be correlated with the protection of MT on hippocampal CA1 neurons.