Previous studies have also shown that subchronic administration of N/OFQ or N/OFQ analogues significantly reduces ethanol self-administration in genetically selected alcohol preferring Marchigian Sardinian msP rats (Ciccocioppo et al., 2004; Economidou et al., 2006). In contrast, in nonselected Wistars tested under the same experimental conditions, N/OFQ did not alter ethanol consumption (Economidou et al., 2008). In situ hybridization studies revealed higher expression levels of N/OFQ and NOP receptor mRNA in numerous brain areas of msP compared to Wistar rats. In particular, significantly higher levels of N/OFQ mRNA have been found in the bed nucleus of the stria terminalis (BNST) and central amygdala (CeA) of msP rats; again, in these animals, the NOP receptor transcript was higher in the CeA and the basolateral amygdala (BLA). Receptor autoradiography revealed that these gene expression changes were accompanied by significant increases in NOP receptor binding within several brain areas, including the CeA, the BNST, the ventral tegmental area, and several cortical structures (Economidou et al., 2008).
