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NEUROPHARMACOLOGY
Department of Experimental and Clinical Medicine, Section of Pharmacology and Istituto Nazionale di Neuroscience (A.R., E.C.G., G.M., B.S., S.Z., D.R., G.C.) and Department of Pharmaceutical Science and Biotechnology Center (C.T.) University of Ferrara, Ferrara, Italy; and Department of Experimental Medicine and Public Health (R.C.), University of Camerino, Camerino, Italy
The excellent pharmacological profile displayed by the selective nociceptin/orphanin FQ (N/OFQ) peptide (NOP) receptor antagonist SB-612111 [()-cis-1-methyl-7-[[4-(2,6-dichlorophenyl)piperidin-1-yl]methyl]-6,7,8,9-tetrahydro-5H-benzocyclohepten-5-ol] in vitro prompted us to investigate the actions of this compound in vivo. In the mouse tail withdrawal assay, SB-612111 given i.p. up to 3 mg/kg did not modify per se tail withdrawal latencies but was able to prevent the pronociceptive and the antinociceptive action of 1 nmol of N/OFQ given i.c.v. and i.t., respectively. In food intake studies performed in sated mice, SB-612111 (1 mg/kg i.p.) had no effect on food consumption but fully prevented the orexigenic effect of 1 nmol of N/OFQ i.c.v. In 17-h food-deprived mice, the opioid receptor antagonist naltrexone (1 mg/kg s.c.), but not SB-612111 (1 and 10 mg/kg i.p.), produced a statistically significant reduction of food intake. In the mouse forced swimming and tail suspension tests, SB-612111 (110 mg/kg) reduced immobility time. The antidepressant-like effect elicited by SB-612111 in the forced swimming test was reversed by the i.c.v. injection of 1 nmol of N/OFQ and no longer evident in mice knockout for the NOP receptor gene. In conclusion, the present findings demonstrate that SB-612111 behaves in vivo as a potent and selective NOP antagonist and suggest that the N/OFQ-NOP receptor endogenous system plays an important role in regulating mood-related behaviors. The use of SB-612111 in future pathophysiological studies will certainly contribute to define the therapeutic potential of selective NOP receptor antagonists in different disease areas.
Address correspondence to: Dr. Girolamo Calò, Department of Experimental and Clinical Medicine, Section of Pharmacology, via Fossato di Mortara 19, 44100 Ferrara, Italy. E-mail: g.calo{at}unife.it