Reduction in OFQ/N1–17-Induced Analgesia Elicited From the Amygdala by Pretreatment With Mu, Kappa, and Delta Opioid Antagonists in Rats
The heptadecapeptide, orphanin FQ/nociceptin (OFQ/N1–17) binds with high affinity to the ORL-1/KOR-3 opioid receptor, but binds poorly with classic opioid receptors. Although it displays both hyperalgesic and analgesic responses following ventricular administration, OFQ/N1–17 only produces analgesia following administration into the amygdala. The present study examined whether amygdala pretreatment with equimolar (0.27–2.7 nmol) doses of either general (naltrexone), μ (β-funaltrexamine), κ (nor-binaltorphamine), or δ (naltrindole) opioid receptor antagonists would alter OFQ/N1–17-induced analgesia elicited from the amygdala as measured by the tail flick test in rats. OFQ/N1–17 produced a modest analgesia across a 60-min time course that was significantly reduced by pretreatment with either general, μ, κ, or δ opioid antagonists. Given that the amygdala, and particularly the medial amygdaloid nucleus, is a common site at which dense distributions of the ORL-1/KOR-3 receptor are found together with dense distributions of classic μ, κ, and δ opioid receptors, these data suggest physiological interactions in the amygdala between neurons with classic opioid receptors and neurons with the ORL-1/KOR-3 receptor in mediating OFQ/N1–17-induced analgesia in the amygdala.
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Document Type: Research Article
Affiliations: Neuropsychology Doctoral Sub-Program and Department of Psychology, Queens College, City University of New York
Publication date: December 1, 2001
More about this publication?
- From 2003 onwards, published as Reviews in Analgesia