Figure 1.

Increase of glutamate uptake in hippocampal synaptosomes during withdrawal in chronicmorphine-treatedrats. The results were presented as mean±SEM of four to six rats per group, each tested by triplicate reconstitutions. *p < 0.05 and **p < 0.01 compared with the saline group. A, B, Effect of chronic morphine treatment (Mor) and saline treatment (Sal) on different brain regions. After subcutaneous injection of morphine (10 mg/kg) twice per day at 12 hr intervals for 10 d, the glutamate uptake in the synaptosomal particles of hippocampus (Hip) was increased significantly, whereas that of other regions such as prefrontal cortex (PC), cerebellum (Cer), and brainstem (BS) were decreased. C, Glutamate uptake in synaptosomal particles of hippocampus was increased time dependently after 1,5,10 dmorphine exposure.D, The glutamate uptake was increased to the highest level 12 hr after the termination of morphine treatment and then decreased gradually 24, 36, and 48 hr later. E, Reexposure of the animals to morphine (10 mg/kg) at the 12 hr time point restored the increased glutamate uptake to the normal level 1 hr later, and the increase was initiated again by additional treatment of naloxone (Nal) (1 mg/kg).