Although opiates have long been known to' alter many aspects of synaptic transmission, the molecular mechanism of its effects on neurotransmitter release and reuptake systems at synapses remains further investigated. Here we showed that morphine withdrawal caused a drastic increase of synaptosomal glutamate uptake of hippocampus in chronic morphine-treated rats, which might be produced by altering the number of functional transporters GLT1. The increase in glutamate uptake and the translocation