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Neuroreport. 2000 Aug 3;11(11):2369-72.

The nociceptin/orphanin FQ receptor antagonist, [Nphe1]NC(1-13)NH2, potentiates morphine analgesia.

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Department of Experimental and Clinical Medicine, University of Ferrara, Italy.


Nociceptin/orphanin FQ (NC) and its receptor (OP4) represent a novel peptide/receptor system which has been implicated in the regulation of various central functions, including pain. The aim of the present study was to explore the involvement of the endogenous NC/OP4 system in the modulation of opioid analgesia using the selective OP4 receptor antagonist [Nphe1]NC(1-13)NH2. Experiments were performed in mice exposed to acute as well as chronic treatment with morphine. [Nphe1]NC(1-13)NH2, injected i.c.v. at 30 nmol, strongly potentiated the analgesic effect of supraspinal morphine (1 nmol, i.c.v.) while it only slightly increased the antinociceptive activity of morphine given systemically (5 mg/kg, s.c.). [Nphe1]NC(1-13)NH, (30 nmol, i.c.v.) also potentiated morphine analgesia in mice made tolerant to the opiate (30 mg/kg/day for 4 days). These findings implicate the endogenous NC signaling as a modulator of morphine analgesia and tolerance.

[Indexed for MEDLINE]

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