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The sigma1 (sigma1) receptor constitutes a particular target of cocaine believed to be involved in some of its behavioral effects. In the present study, its involvement in the rewarding effect of cocaine was examined using the conditioned place preference (CPP) procedure. CPP was induced in C57Bl/6 mice injected repeatedly with cocaine (20 mg/kg, i.p.). The selective sigma1 receptor antagonists NE-100 and BD1047 (1-10 mg/kg, i.p.) significantly attenuated or blocked the cocaine-induced CPP. Animals treated centrally with a sigma1 receptor antisense oligodeoxynucleotide failed to develop cocaine-induced CPP, unlike mismatch controls. The sigma1 receptor thus appears to be critically involved in the development of the cocaine-induced CPP and, in consequence, may constitute a promising approach to blocking cocaine reward.

This study examined whether nociceptin/orphanin FQ (NC), the endogenous ligand of the opioid receptor-like1 (ORL1) receptor, can block drug-seeking behavior induced by foot-shock stress. Male Wistar rats were trained to operantly self-administer ethanol or cocaine, and then subjected to daily extinction training until responding ceased. Subsequent exposure to 15 min of intermittent footshock elicited robust reinstatement of responding at the previously drug-paired lever. NC (0.1-2.0 microg; i.c.v.) significantly inhibited the effects of footshock stress on ethanol- but not cocaine-seeking behavior. The results support the hypothesis that the NC system participates in the regulation of behavioral responses to stress, and that drugs interacting with NC receptors may have therapeutic potential for the treatment of stress-induced alcohol-seeking behavior and relapse.