Activity and cyclic AMP-dependent regulation of nociceptin/orphanin FQ gene expression in primary neuronal and astrocyte cultures.

The regulation of nociceptin/orphanin FQ (N/OFQ) gene expression by neuronal activity and by activation of the cyclic AMP signaling pathway in primary neuronal and astroglial cultures is described. Neuronal activity mimicked by veratridine-mediated depolarization profoundly increased N/OFQ gene expression in primary striatal neurons. Calcium entry through L-type, but not N-type, voltage-sensitive calcium channels activated by depolarization appears to be involved, because nitrendipine and nifedipine, but not omega-conotoxin, reduced the induction of N/OFQ expression by veratridine. A selective inhibitor of calcium/calmodulin kinases (KN-62) also antagonized the depolarization-induced increase in N/OFQ mRNA levels, suggesting a role for these enzymes in the activity-dependent induction of N/OFQ gene expression. Constitutively expressed transcription factors may mediate N/OFQ gene expression levels, because veratridine induction of N/OFQ transcription was insensitive to the protein synthesis inhibitor cycloheximide. Regulation of N/OFQ gene expression by depolarization and cyclic AMP is not restricted to striatal neurons, because similar regulation was also observed in neuronal cultures derived from the cerebral cortex. Veratridine did not increase N/OFQ mRNA levels in primary astrocyte cultures; however, elevated intracellular cyclic AMP levels lead to a dramatic, 30-fold induction of N/OFQ mRNA levels in these cells.