Chronic deep brain stimulation in the rat nucleus accumbens and its effect on morphine reinforcement

In order to explore a novel method for the treatment of drug abuse, we evaluated the effect of chronic deep brain stimulation (DBS) of the rat nucleus accumbens (NAc) on morphine reinforcement, using a DBS apparatus and an implant method we developed. Thirty-two adult rats weighing 240-260 g were divided into three groups, which included a DBS group (n = 10, administration of surgery, morphine and DBS), a sham DBS group (n = 12, administration of surgery and morphine) and a control group (n = 10, administration of physiological saline). The DBS electrode was stereotaxically implanted into the core of unilateral NAc and connected to an implantable pulse generator. Then, they were fixed to the rat skull. One week later, the rats in each group were intraperitoneally injected with morphine at an increasing dose (10-60 mg/kg) once daily. The rats in the DBS group were administered a 130-Hz high-frequency stimulation (HFS) once daily. A 900-second conditioned place preference (CPP) paradigm was used for determining the effect of electrical stimulation on morphine reinforcement in rats. The data showed that 7-10 days later, the preference score of the DBS group was significantly lower than that of the sham DBS group. The results suggest that chronic HFS of the rat NAc can block CPP induced by morphine and attenuate morphine reinforcement.