The rewarding effect of aggression is reduced by nucleus accumbens dopamine receptor antagonism in mice.
BACKGROUND
Dopamine (DA) receptors within the nucleus accumbens (NAc) are implicated in the rewarding properties of stimuli. Aggressive behavior can be reinforcing but the involvement of NAc DA in the reinforcing effects of aggression has yet to be demonstrated.


OBJECTIVE
To microinject DA receptor antagonists into the NAc to dissociate their effects on reinforcement from their effects on aggressive behavior and general movement.


METHODS
Male Swiss Webster mice were implanted with guide cannulae aimed for the NAc and tested for aggressive behavior in a resident-intruder procedure. Aggressive mice were then conditioned on a variable-ratio 5 (VR-5) schedule with presentation of the intruder as the reinforcing event. The D1- and D2-like receptor antagonists SCH-23390 and sulpiride were microinfused (12-50 ng) before the mice responded on the VR-5 schedule and attacked the intruder. Open-field activity was also determined following the highest doses of these drugs.


RESULTS
SCH-23390 and sulpiride dose-dependently reduced VR responding but did not affect open-field activity. The 50-ng SCH-23390 dose suppressed response rates by 40% and biting behaviors by 10%; other aggressive behaviors were not affected. The 25 and 50 ng sulpiride doses almost completely inhibited VR responding; the 50-ng dose suppressed biting by 50%.


CONCLUSIONS
These results suggest that both D1- and D2-like receptors in the ventral striatum are involved in the rewarding properties of aggression, but that D1-like receptors may be related to the motivation to earn reinforcement as opposed to aggressive behavior.
Couppis
Maria H
MH
Vanderbilt Kennedy Center, Vanderbilt University, Nashville, TN 37204, USA.
Kennedy
Craig H
CH
D000374:Aggression / Q000187:drug effects* / Q000502:physiology; D000378:Agonistic Behavior / Q000187:drug effects / Q000502:physiology; D000818:Animals; D001552:Benzazepines / Q000494:pharmacology*; D001931:Brain Mapping; D003216:Conditioning, Operant / Q000187:drug effects* / Q000502:physiology; D018492:Dopamine Antagonists / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D005106:Exploratory Behavior / Q000187:drug effects; D008297:Male; D051379:Mice; D008845:Microinjections; D009042:Motivation; D009043:Motor Activity / Q000187:drug effects / Q000502:physiology; D009714:Nucleus Accumbens / Q000187:drug effects* / Q000502:physiology; D017447:Receptors, Dopamine D1 / Q000187:drug effects* / Q000502:physiology; D017448:Receptors, Dopamine D2 / Q000187:drug effects* / Q000502:physiology; D012055:Reinforcement Schedule; D012201:Reward; D012931:Social Environment; D013469:Sulpiride / Q000494:pharmacology*
D001552:Benzazepines; D018492:Dopamine Antagonists; D017447:Receptors, Dopamine D1; D017448:Receptors, Dopamine D2; D013469:Sulpiride