Effect of nociceptin/orphanin FQ on food intake in rats that differ in diet preference.
Nociceptin/orphanin FQ (N/OFQ) is an agonist of the ORL1 receptor. Despite homology with opioids, it does not bind to opioid receptors. Recent studies have shown that centrally administered N/OFQ increases food intake in a manner similar to opioid peptides; its effect is naloxone-reversible. Opioids appear to mediate "palatability/reward"-dependent feeding: Opioid agonists increase, while antagonists decrease, the intake of preferred diets. The current project was designed to elucidate whether the effect of N/OFQ on the consumption of preferred foods resembles that of opioid peptides. Rats had a constant access for 2 weeks to two palatable (high sucrose and high fat) diets, and their baseline preferences were established. Based on these preferences, animals were divided into three groups: fat preferrers, sucrose preferrers, and "neutrals". On the experimental day, rats received an intracerebroventricular injection of N/OFQ. Intriguingly, in fat-preferring rats, N/OFQ stimulated the intake of each of the two diets. It had no effect, however, on the consumption of either diet or cumulative food intake in sucrose-preferring or "neutral" animals. Our results reveal that N/OFQ, unlike opioids, does not increase the intake of preferred diets. Thus, it does not seem to mediate "palatability/reward"-driven feeding. Noteworthy, N/OFQ appears to cause hyperphagia only in fat-preferring rats.
Olszewski
Pawel K
PK
Minnesota Obesity Center, Veterans Affairs Medical Center, Minneapolis, MN 55417, USA.
Grace
Martha K
MK
Sanders
Jeffrey B
JB
Billington
Charles J
CJ
Levine
Allen S
AS
D000818:Animals; D004032:Diet; D004041:Dietary Fats; D004435:Eating / Q000187:drug effects*; D002149:Energy Intake / Q000187:drug effects; D005518:Food Preferences / Q000187:drug effects*; D007276:Injections, Intraventricular; D008297:Male; D018847:Opioid Peptides / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D011957:Receptors, Opioid / Q000819:agonists*; D012201:Reward; D013395:Sucrose; D000094942:Nociceptin Receptor; D000097629:Nociceptin
D004041:Dietary Fats; D018847:Opioid Peptides; D011957:Receptors, Opioid; D013395:Sucrose; D000094942:Nociceptin Receptor; D000097629:Nociceptin; C000722285:Oprl1 protein, rat