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Updated: Jul 18, 2026
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Operant Sensation Seeking in the Mouse
Published on: November 10, 2010
Selective reward deficit in mice lacking beta-endorphin and enkephalin
Michael D Hayward1, John E Pintar, Malcolm J Low
1The Vollum Institute, Oregon Health and Science University, Portland, Oregon 97201, USA.
Summary
Both beta-endorphin and enkephalin are crucial for motivation to work for food rewards. Their absence reduces this drive, particularly when not hungry, impacting food
Area of Science:
- Neuroscience
- Behavioral Science
- Opioid Research
Background:
- Endogenous opioids' roles in reward are unclear due to receptor non-selectivity.
- Identifying specific opioid peptide contributions to motivation is challenging.
Purpose of the Study:
- To investigate the roles of beta-endorphin and enkephalin in motivated behavior.
- To determine if these peptides influence the incentive value of food rewards.
Main Methods:
- Utilized beta-endorphin and enkephalin knockout mice.
- Employed a progressive ratio schedule to measure instrumental behavior for food.
- Tested responses in both deprived and non-deprived states.
Main Results:
- Loss of either beta-endorphin or enkephalin reduced instrumental responding for food.
- Mice lacking both opioids showed similar deficits.
- Reduced responding was observed only in non-deprived mice.
- No effect on sweet taste preference was found.
Conclusions:
- Both beta-endorphin and enkephalin positively contribute to the motivation for food.
- These peptides likely alter food hedonics rather than energy homeostasis.
- Findings highlight the specific roles of these opioids in reward-seeking behavior.
