Changes of extracellular amino acids levels in related brain regions of rats with psychological dependence on morphine

Abstract

Objective To investigate the changes in the levels of extracellular glutamate(Glu)and gamma-aminobutyric acid(GABA)in the nucleus accumbens(NAc),ventral pallidum(vP)and ventral tegmental area(VTA)of rats with psychological dependence on morphine.Methods Eighteen Wistar rats were randomized into control group(n=8)and morphine group(n=10).Morphine hydrochloride was injected subcutaneously in rats in the morphine group for 10 days,followed by conditioned place preference(CPP)training,and the CPP behavior of the rats was evaluated after disappearance of physical morphine dependence.Sodium chloride solution was injected subcutaneously in rats in the control group.One week after morphine withdrawal,microdialysis probes were placed into the NAc,VP and VTA of the rats under anesthesia,and the levels of extracellular Glu and GABA in the microdialysates were determined using high-perforance liquid chromatography(HPLC).Results Compared with the control group,the rats in the morohine group showed significantly increased levels of extracellular Glu in the NAc(P＜0.05),while the levels of extracellular Glh and GABA remained unchanged in the VP and VTA.Conclusion Glu plays an important role in the maintenance of psychological morphine dependence. Key words: Morphine; Psychological dependence; Nucleus accurnbens; Glutamate