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 n euronal activity and by activation of the cyclic AMP signaling pathway in primary neuronal and astroglial cultures is described. Neuronal ac tivity mimicked by veratridine-mediated depolarization profoundly incr eased N/OFQ gene expression in primary striatal neurons. Calcium entry through L-type, but not N-type, voltage-sensitive calcium channels ac tivated by depolarization appears to be involved, because nitrendipine and nifedipine, but not omega-conotoxin, reduced the induction of N/O FQ expression by veratridine. A selective inhibitor of calcium/calmodu lin kinases (KN-62) also antagonized the depolarization-induced increa se in N/OFQ mRNA levels, suggesting a role for these enzymes in the ac tivity-dependent induction of N/OFQ gene expression. Constitutively ex pressed 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 neu ronal cultures derived from the cerebral cortex. Veratridine did not i ncrease N/ OFQ mRNA levels in primary astrocyte cultures; however, ele vated intracellular cyclic AMP levels lead to a dramatic, 30-fold indu ction of N/OFQ mRNA levels in these cells.