title: Dopamine in the nucleus accumbens modulates the memory of social defeat in Syrian hamsters (Mesocricetus auratus).
abstract: Conditioned defeat (CD) is a behavioral response that occurs in Syrian hamsters after they experience social defeat. Subsequently, defeated hamsters no longer produce territorial aggression but instead exhibit heightened levels of avoidance and submission, even when confronted with a smaller, non-aggressive intruder. Dopamine in the nucleus accumbens is hypothesized to act as a signal of salience for both rewarding and aversive stimuli to promote memory formation and appropriate behavioral responses to significant events. The purpose of the present study was to test the hypothesis that dopamine in the nucleus accumbens modulates the acquisition and expression of behavioral responses to social defeat. In Experiment 1, bilateral infusion of the non-specific D1/D2 receptor antagonist cis(z)flupenthixol (3.75 μg/150 nl saline) into the nucleus accumbens 5 min prior to defeat training significantly reduced submissive and defensive behavior expressed 24h later in response to a non-aggressive intruder. In Experiment 2, infusion of 3.75 μg cis-(Z)-flupenthixol 5 min before conditioned defeat testing with a non-aggressive intruder significantly increased aggressive behavior in drug-infused subjects. In Experiment 3, we found that the effect of cis-(Z)-flupenthixol on aggression was specific to defeated animals as infusion of drug into the nucleus accumbens of non-defeated animals did not significantly alter their behavior in response to a non-aggressive intruder. These data demonstrate that dopamine in the nucleus accumbens modulates both acquisition and expression of social stress-induced behavioral changes and suggest that the nucleus accumbens plays an important role in the suppression of aggression that is observed after social defeat.
authors.affiliation: Neuroscience Institute, Morehouse School of Medicine, Atlanta, GA 30310, USA.
authors.forename: C L
authors.initials: CL
authors.lastname: Gray
authors.affiliation: Neuroscience Institute, Georgia State University, Atlanta, GA 30302, USA.
authors.forename: A
authors.initials: A
authors.lastname: Norvelle
authors.affiliation: Neuroscience Institute, Georgia State University, Atlanta, GA 30302, USA.
authors.forename: T
authors.initials: T
authors.lastname: Larkin
authors.affiliation: Neuroscience Institute, Georgia State University, Atlanta, GA 30302, USA. Electronic address: khuhman@gsu.edu.
authors.forename: K L
authors.initials: KL
authors.lastname: Huhman
mesh_terms: D000374:Aggression / Q000187:drug effects / Q000502:physiology; D000818:Animals; D002408:Catheters, Indwelling; D003213:Conditioning, Psychological / Q000187:drug effects / Q000502:physiology; D004291:Dominance-Subordination; D004298:Dopamine / Q000378:metabolism; D018492:Dopamine Antagonists / Q000494:pharmacology; D005239:Fear / Q000187:drug effects / Q000502:physiology; D005475:Flupenthixol / Q000494:pharmacology; D008297:Male; D008568:Memory / Q000187:drug effects / Q000502:physiology*; D008647:Mesocricetus; D009714:Nucleus Accumbens / Q000187:drug effects / Q000502:physiology*; D017447:Receptors, Dopamine D1 / Q000037:antagonists & inhibitors / Q000378:metabolism*; D017448:Receptors, Dopamine D2 / Q000378:metabolism*
chemical_list: D018492:Dopamine Antagonists; D017447:Receptors, Dopamine D1; D017448:Receptors, Dopamine D2; D005475:Flupenthixol; D004298:Dopamine
keywords: Aggression; Conditioned defeat; Fear learning; Social stress