80 Hz electrical stimulus to nucleus accumbens influencing the formation of conditioned place preference induced by morphine in rats / 第二军医大学学报

ABSTRACT

Objective: To investigate the influence of 80 Hz electrical stimulus to nucleus accumbens (NAc) on the formation of conditioned place preference (CPP) induced by morphine in rats. Methods: Thirty male SD rats were evenly randomized into 3 groups the morphine stimulation group, morphine-fake stimulation group, and normal control group. The CPP test was carried out under different situations in 3 groups. Five steps were included in the morphine stimulation and morphine-fake stimulation groups, namely, the pre-test, surgery, training, stimulation or fake stimulation, and test steps. Four steps were included in the control group, namely, the pre-test, surgery, training, and test steps. During the training step, rats in morphine stimulation group and morphine-fake stimulation were respectively injected with morphine and normal saline by turns everyday, and those in normal control group were injected with normal saline twice a day. During the stimulation step, 80 Hz electrical stimulus was applied to the NAc in the morphine stimulation group and the fake-stimulation group received no stimulation. The average stay periods in the white case during the period of pre-test and test were recorded and compared in the 3 groups. Results: The average stay in the white case of morphine-fake stimulation group was longer than that before training and that of the saline control group at the same step (P<0. 01), suggesting that the model of morphine-induced psychological dependence was successfully established. The average stay of morphine stimulation group was longer than that of morphine-fake stimulation group (P<0. 01), indicating that the electrical simulation greatly enhanced the drug-seeking behaviors of rats. Conclusion: 80 Hz electrical stimulation of bilateral NAc can obviously promote the formation of morphine-induced CPP behaviors in rats, indicating that the morphine-induced psychological dependence is strengthened under 80 Hz electrical stimulus.