ABSTRACT
Objective To evaluate the role of μ-δ heterodimer in down-regulation of the expression of excitatory amino acid transporter 3 (EAAT3) in hippocampi caused by reinstatement of morphine-induced conditioned place preference (CPP) in rats.Methods Thirty-two healthy clean-grade male Sprague-Dawley rats,weighing 200-240 g,were assigned into 4 groups (n =8 each) using a random number table method:control group (group C),extinction group (group E),reinstatement group (group R) and reinstatement plus interference plasmid group (group RI).The model of morphine-induced CPP was established,and extinction of CPP was gradually induced by stopping administration.A small dose of morphine 5 mg/kg was intraperitoneally injected again to induce CPP reinstatement,and dwell time around the medicine box was recorded.μ-δ heterodimer interference plasmid 5 μl was injected into the lateral cerebral ventricle after successful establishment of CPP model in group RI.The content of glutamate (Glu) in hippocampi was measured using high-performance liquid chromatography.The EAAT3 expression in hippocampal CA1 and CA3 regions was detected using Western blot.Results Compared with group C,no significant change was found in the dwell time around the medicine box or content of Glu in hippocampi (P＞0.05),and the expression of EAAT3 in hippocampal CA1 and CA3 regions was significantly up-regulated in group E,and the dwell time around the medicine box was significantly prolonged,the content of Glu in hippocampi was increased (P＜0.05),and no significant change was found in the expression of EAAT3 in hippocampal CA1 and CA3 regions in group R (P＞0.05).Compared with group E,the dwell time around the medicine box was significantly prolonged,the content of Glu in hippocampi was increased,and the expression of EAAT3 in hippocampal CA1 and CA3 regions was down-regulated in group R (P＜0.05).Compared with group R,the dwell time around the medicine box was significantly shortened,the content of Glu in hippocampi was decreased,and the expression of EAAT3 in hippocampal CA 1 and CA3 regions was upregulated in group RI (P＜0.05).Conclusion μ-δ heterodimer is involved in down-regulation of EAAT3 expression in the hippocampus caused by reinstatement of morphine-induced CPP in rats.