Morphine reduces the interest for natural rewards.

Alessandro Piccin, Gilles Courtand, Angelo Contarino
Psychopharmacology. 2022-04-08; :
DOI: 10.1007/s00213-022-06131-7

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Piccin A(1)(2), Courtand G(1)(2), Contarino A(3)(4).

Author information:
(1)Université de Bordeaux, INCIA, UMR 5287, Bordeaux, France.
(2)CNRS, INCIA, UMR 5287, Bordeaux, France.
(3)Université de Bordeaux, INCIA, UMR 5287, Bordeaux, .
(4)CNRS, INCIA, UMR 5287, Bordeaux, France. .

RATIONALE: Alongside a pathological, excessive, motivation for substances of
abuse, substance use disorder (SUD) patients often show a dramatic loss of
interest for naturally rewarding activities, such as positive peer social
interaction and food intake. Yet, pre-clinical evidence of the latter SUD
features remains scarce and inconsistent.

OBJECTIVES: In the current study, we investigated the effect of non-rewarding and
rewarding doses of morphine upon social behaviour, motivation for and intake of
palatable food, in male and female C57BL/6J mice.

METHODS: First, the rewarding effects of two relatively low morphine doses (1.25
and 2.5 mg/kg) were assessed using a newly established single substance
administration/conditioning trial conditioned place preference (CPP) paradigm.
Then, morphine (1.25 and 2.5 mg/kg) effects upon social behaviour, motivation for
and intake of palatable food were examined by the three-chamber (3-CH), an
operant behaviour and a palatable food preference test, respectively.

RESULTS: Morphine (2.5 mg/kg) induced CPP in both male and female mice, whereas
morphine (1.25 mg/kg) induced CPP only in female mice. Both morphine doses (1.25
and 2.5 mg/kg) reduced sociability, motivation for and intake of palatable food
in male and female mice, independently of cognitive function or locomotor
activity.

CONCLUSIONS: Female mice were more sensitive than male mice to the rewarding
effects of morphine. Moreover, both a non-rewarding and a rewarding dose of
morphine impaired the interest for naturally rewarding activities, indicating
that brain reward systems might be more sensitive to the deleterious than to the
rewarding effects of substances of abuse.

Auteurs Bordeaux Neurocampus