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Hedonic drinking engages a supra-spinal inhibition of thermal nociception in adult rats

Research output: Contribution to journalArticle

Original languageEnglish
Pages (from-to)1059-1069
Number of pages11
JournalPAIN
Volume160
Issue number5
Early online date1 May 2019
DOIs
DateAccepted/In press - 27 Dec 2018
DateE-pub ahead of print - 1 May 2019
DatePublished (current) - 1 May 2019

Abstract

The taste of sucrose is commonly used to provide pain relief in newborn humans and is innately analgesic to neonatal rodents. In adulthood, sucrose remains a strong motivator to feed, even in potentially hazardous circumstances (ie, threat of tissue damage). However, the neurobiological mechanisms of this endogenous reward-pain interaction are unclear. We have developed a simple model of sucrose drinking-induced analgesia in Sprague-Dawley rats (6-10 weeks old) and have undertaken a behavioral and pharmacological characterization using the Hargreaves' test of hind-paw thermal sensitivity. Our results reveal an acute, potent, and robust inhibitory effect of sucrose drinking on thermal nociceptive behaviour that unlike the phenomenon in neonates is independent of endogenous opioid signalling and does not seem to operate through classical descending inhibition of the spinal cord circuitry. Experience of sucrose drinking had a conditioning effect whereby the apparent expectancy of sucrose enabled water alone (in euvolemic animals) to elicit a short-lasting placebo-like analgesia. Sweet taste alone, however, was insufficient to elicit analgesia in adult rats intraorally perfused with sucrose. Instead, the sucrose analgesia phenomenon only appeared after conditioning by oral perfusion in chronically cannulated animals. This sucrose analgesia was completely prevented by systemic dosing of the endocannabinoid CB1 receptor antagonist rimonabant. These results indicate the presence of an endogenous supraspinal analgesic circuit that is recruited by the context of rewarding drinking and is dependent on endocannabinoid signalling. We propose that this hedonic sucrose-drinking model may be useful for further investigation of the supraspinal control of pain by appetite and reward.

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    Rights statement: This is the author accepted manuscript (AAM). The final published version (version of record) is available online via Wolters Kluwer at https://journals.lww.com/pain/Fulltext/2019/05000/Hedonic_drinking_engages_a_supraspinal_inhibition.9.aspx . Please refer to any applicable terms of use of the publisher.

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