TY - JOUR
T1 - Lipopolysaccharide reduces incentive motivation while boosting preference for high reward in Mice
AU - Vichaya, Elisabeth G.
AU - Hunt, Sarah C.
AU - Dantzer, Robert
N1 - Funding Information:
This work was supported by the University of Texas MD Anderson Cancer Center and grants from the National Institute of Neurological Diseases and Stroke of the National Institutes of Health (Grants R01 NS073939; R01 NS074999). The content is solely the responsibility of the authors and does not necessarily represent the official view of the National Institutes of Health. RD consulted for Ironwood Pharma (Cambridge, MA).
PY - 2014/11
Y1 - 2014/11
N2 - Inflammation has been implicated in the development of various psychiatric disorders, including depression. However, the neurobehavioral mechanism involved in this relationship remains elusive. This gap in knowledge may best be filled by evaluating elementary neurobehavioral units affected by inflammation rather than behavioral changes in conventional animal tests of depression. To this end, the current study used a concurrent choice paradigm to evaluate inflammation-induced motivational changes. Male C57BL/6J mice (n=27) were food restricted to between 85 and 90% of their free-feeding weight and were trained to perform a concurrent choice task where they nose-poked for grain rewards on a fixed ratio (FR) 1 schedule (low effort/low reward) and chocolate-flavored rewards on a FR-10 schedule (high effort/high reward). A counterbalanced-within subjects design was used. A single intraperitoneal injection of 0.33 mg/kg lipopolysaccharide (LPS) was used to induce peripheral inflammation. Twenty-four hours after LPS administration, mice showed a reduction in the total number of nose pokes. A proportionally greater reduction in nose pokes was observed for grain, resulting in an increase in percent chocolate pellets earned. These behavioral changes cannot be explained by reduced appetite as feeding before the test led to a similar increase in percent chocolate pellets earned but without any decrease in responding. These results indicate that inflammation modulates incentive motivation by affecting willingness to exert effort for reward and not by reducing sensitivity to reward.
AB - Inflammation has been implicated in the development of various psychiatric disorders, including depression. However, the neurobehavioral mechanism involved in this relationship remains elusive. This gap in knowledge may best be filled by evaluating elementary neurobehavioral units affected by inflammation rather than behavioral changes in conventional animal tests of depression. To this end, the current study used a concurrent choice paradigm to evaluate inflammation-induced motivational changes. Male C57BL/6J mice (n=27) were food restricted to between 85 and 90% of their free-feeding weight and were trained to perform a concurrent choice task where they nose-poked for grain rewards on a fixed ratio (FR) 1 schedule (low effort/low reward) and chocolate-flavored rewards on a FR-10 schedule (high effort/high reward). A counterbalanced-within subjects design was used. A single intraperitoneal injection of 0.33 mg/kg lipopolysaccharide (LPS) was used to induce peripheral inflammation. Twenty-four hours after LPS administration, mice showed a reduction in the total number of nose pokes. A proportionally greater reduction in nose pokes was observed for grain, resulting in an increase in percent chocolate pellets earned. These behavioral changes cannot be explained by reduced appetite as feeding before the test led to a similar increase in percent chocolate pellets earned but without any decrease in responding. These results indicate that inflammation modulates incentive motivation by affecting willingness to exert effort for reward and not by reducing sensitivity to reward.
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U2 - 10.1038/npp.2014.141
DO - 10.1038/npp.2014.141
M3 - Article
C2 - 24917202
AN - SCOPUS:84939876942
SN - 0893-133X
VL - 39
SP - 2884
EP - 2890
JO - Neuropsychopharmacology
JF - Neuropsychopharmacology
IS - 12
ER -