Abstract:

Objective To investigate the changes of levels of glutamate(Glu) and gammaaminobutyric acid(GABA) in nucleus accumbens(NAc), ventral pallidum(VP) and ventral tegmental area(VTA) after high frequency electrical stimulation of NAc in morphine psychic dependent rats, and illustrate the mechanism of high frequency electrical stimulation treatment of drug psychic dependence. Methods Morphine hydrochloride was injected subcutaneously in Wistar rats for 10 days(3 times per day), sodium chloride solution was injected subcutaneously in rats of control group. At the 7th day after withdrawal of morphine, Concentric bipolar electrodes were stereotaxically implanted into the NAc and microdialysis probes were unilaterally placed into NAc, VP and VTA of rats after anesthesia, the microdialysates before stimulation and after stimulation were collected. The levels of extracellular Glu and GABA in microdialysates were determined by high-performance liquid chromatography(HPLC). In control group, only stimulating electrodes were implanted, stimulation was not proceeded.Results The levels of extracellular Glu in NAc increased in morphine group. During and after stimulation of NAc, the levels of extracellular Glu in NAc and VTA decreased, but the levels of extracellular GABA did not change; The levels of extracellular Glu and GABA in VP did not change. Conclusion Glu is an important factor to maintain psychic dependence, and high frequency electrical stimulation can induce decrease in extracellular Glu levels in NAc and VTA to diminish morphine psychic dependence.

Key words: morphine, psychic dependence, nucleus accumbens, high frequency electrical stimulation, glutamate