| Title | Analgesia accompanying food consumption requires ingestion of hedonic foods. | | Author(s) | Foo H, Mason P | | Institution | Department of Neurobiology and Committee on Neurobiology, University of Chicago, Chicago, Illinois 60637, USA. | | Source | J Neurosci 2009 Oct 14; 29(41):13053-62. | | MeSH | Analgesia
Analgesics, Non-Narcotic
Analysis of Variance
Animals
Avoidance Learning
Behavior, Animal
Cacao
Conditioning, Classical
Conditioning, Operant
Eating
Electromyography
Feeding Behavior
Food Preferences
Hot Temperature
Hypnotics and Sedatives
Lipopolysaccharides
Male
Pentobarbital
Quinine
Rats
Rats, Sprague-Dawley
Reaction Time
Sweetening Agents
| | Abstract | Animals eat rather than react to moderate pain. Here, we examined the behavioral, hedonic, and neural requirements for ingestion analgesia in ad libitum fed rats. Noxious heat-evoked withdrawals were similarly suppressed during self-initiated chocolate eating and ingestion of intraorally infused water, sucrose, or saccharin, demonstrating that ingestion analgesia does not require feeding motivation, self-initiated food procurement, sucrose, or calories. Rather, food hedonics is important because neither salt ingestion nor quinine rejection elicited analgesia. During quinine-induced nausea and lipopolysaccharide (LPS)-induced illness, conditions when chocolate eating was presumably less pleasurable, analgesia accompanying chocolate consumption was attenuated, yet analgesia during water ingestion was preserved in LPS-injected rats who showed enhanced palatability for water within this context. The dependence of ingestion analgesia on the positive hedonics of an ingestate was confirmed in rats with a conditioned taste aversion to sucrose: after paired exposure to sucrose and LPS, rats no longer showed analgesia during sucrose ingestion but continued to show analgesia during chocolate consumption. Eating pauses tended to occur less often and for shorter durations in the presence of ingestion analgesia than in its absence. Therefore, we propose that ingestion analgesia functions to defend eating from ending. Muscimol inactivation of the medullary raphe magnus blocked the analgesia normally observed during water ingestion, showing the involvement of brainstem endogenous pain inhibitory mechanisms in ingestion analgesia. Brainstem-mediated defense of the consumption of palatable foods may explain, at least in part, why overeating tasty foods is so irresistible even in the face of opposing cognitive and motivational forces. | | Language | eng | | Pub Type(s) | Journal Article
Research Support, N.I.H., Extramural
Research Support, Non-U.S. Gov't
| | PubMed ID | 19828818 |
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