Single and repeated morphine administrations differently regulate expression of N-ethylmaleimide-sensitive factor gene in the rat brain.

The present study investigated the potential effects of single and repeated morphine treatments on gene expression of N-ethylmaleimide-sensitive protein, a key regulatory protein of neurotransmitter release and synaptic plasticity. After a single morphine injection (10 mg/kg), N-ethylmaleimide-sensitive factor gene expression increased significantly in the cortex, hippocampus and periaqueductal gray. In contrast, N-ethylmaleimide-sensitive factor gene expression was not changed after repeated morphine exposures in these brain regions. Sixteen hours after cessation of repeated morphine administration, N-ethylmaleimide-sensitive factor mRNA level increased again to a level approximate to that of the single morphine injection group in the hippocampus, periaqueductal gray and cerebral cortex. These findings suggest that the N-ethylmaleimide-sensitive factor may be involved in the maladaptive changes in the nervous system after opiate treatment.