Gene profiling the rewarding effect of morphine in striatum ans hippocampus

Persistent changes that take place during the development of opioid addiction are thought to be due to adaptive changes in gene expression in the brain. In the present study we used DNA microarrays (Illumina) to analyze the expression of about 45 000 transcripts in the selected brain regions (striatum and hippocampus) of C57Bl/6J mice during the morphine-induced conditioned place preference (CPP) test. Repetitive morphine treatment during morphine conditioning led to an altered expression of 257 genes. Many of these genes coded for heat shock proteins, neuronal transport and kinases including mitogen-activated protein kinases. The observed alterations in the gene transcription resulted from the morphine-induced conditioning rather than CPP test alone. The genes meeting criteria for statistical signifi cance revealed strong correlation coeffi cients with the expression of place preference (measured as increased time spent on the morphine-paired side). These fi ndings suggest that morphine-conditioning induces the persistent changes in gene transcription that correlate with the rewarding behavior. Research supported by Ministry of Science and Education Grant N401 066 31/168.