Nociceptin/orphanin FQ tissue concentration in the rat brain. Effects of repeated ethanol administration at various post-treatment intervals.

The aim of this study was to study short- and long-term effects of repeated ethanol administration on nociceptin/orphanin FQ (N/OFQ) tissue concentrations in rat brain with radioimmunoassay. Animals were given either ethanol (intraperitoneal) or saline for 13 consecutive days. N/OFQ levels were examined at 30 min, 5 days and 21 days after the last dose on day 13. Ethanol-treated rats had significantly decreased N/OFQ tissue concentration in the hippocampus at 30 min after the last dose. N/OFQ levels were decreased in the cingulate cortex at 5 days after cessation of ethanol administration whereas no significant changes were found at 21 days. There were no significant changes in N/OFQ tissue concentrations at any time point studied in the mesolimbic dopamine (DA) system, a brain area associated with ethanol-induced activation. However, the results indicate that repeated ethanol administration may induce short- and long-term changes in N/OFQ tissue concentrations in other brain regions innervated with dopaminergic neurons.