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Morphine reduces the interest for natural rewards
Alessandro Piccin1,2, Gilles Courtand1,2, Angelo Contarino3,4
1Université de Bordeaux, INCIA, UMR 5287, Bordeaux, France.
Psychopharmacology
|April 9, 2022
Summary
Opioid use disorder (OUD) in mice shows reduced interest in social interaction and food. Both rewarding and non-rewarding morphine doses decreased motivation for natural rewards, suggesting brain reward systems are sensitive to drug effects.
Area of Science:
- Neuroscience
- Pharmacology
- Addiction Research
Background:
- Substance use disorder (SUD) is characterized by excessive motivation for drugs and reduced interest in natural rewards.
- Pre-clinical evidence for these SUD features, particularly anhedonia, is limited and inconsistent.
Purpose of the Study:
- Investigate the effects of rewarding and non-rewarding morphine doses on social behavior, food motivation, and intake in male and female mice.
- Assess sex differences in response to morphine's rewarding and anhedonic effects.
Main Methods:
- Conditioned place preference (CPP) assessed rewarding effects of morphine (1.25 and 2.5 mg/kg).
- Three-chamber social interaction test, operant behavior for food motivation, and palatable food preference tests evaluated social behavior and anhedonia.
- Effects were examined independently of cognitive function and locomotor activity.
Main Results:
- Morphine (2.5 mg/kg) induced CPP in both sexes; 1.25 mg/kg induced CPP only in females.
- Both morphine doses reduced sociability, food motivation, and intake in male and female mice.
- These effects were independent of cognitive function or locomotor activity.
Conclusions:
- Female mice exhibit higher sensitivity to morphine's rewarding effects compared to males.
- Both rewarding and non-rewarding morphine doses impair motivation for natural rewards, suggesting heightened sensitivity of reward systems to drug-induced deficits.
- Findings highlight the complex impact of opioids on reward pathways and potential sex differences in addiction vulnerability.
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