Regulation of nociceptin mRNA expression in the septum by dopamine and adenosine systems

Most effects of nociceptin are related to blockade of stress and anxiolytic-like effects. This neuropeptide is highly expressed in septal nuclei, which are involved in response to stressful situations. Dopamine and adenosine may have modulatory effects on stress behaviour by acting on septal neurons. We therefore analysed the regulation of septal nociceptin expression using quantitative in situ hybridization following manipulations of adenosine and dopamine neurotransmission. No difference was observed between wild-type and A2A receptor-deficient mice. In both genotypes, chronic treatments with caffeine, an equipotent A1 and A2A adenosine receptor antagonist, did not significantly modify nociceptin expression. 6-Hydroxydopamine-induced dopamine depletion was also without effect. These results demonstrate that dopamine and adenosine are not involved in the regulation of septal nociceptin expression in spite of the involvement of these three neurotransmitters in stress and anxiety behaviours.