Escalated Aggression after Alcohol Drinking in Male Mice: Dorsal Raphé and Prefrontal Cortex Serotonin and 5-HT1B ReceptorsNeuropsychopharmacology advance online publication 27 February 2008;
A significant minority of individuals engages in escalated levels of aggression after consuming moderate doses of alcohol (Alc). Neural modulation of escalated aggression involves altered levels of serotonin (5-HT) and the activity of 5-HT1B receptors.
The aim of these studies was to determine whether 5-HT1B receptors in the dorsal raphé (DRN), orbitofrontal (OFC), and medial prefrontal (mPFC) cortex attenuate heightened aggression and regulate extracellular levels of 5-HT.
Male mice were trained to self-administer Alc by performing an operant response that was reinforced with a delivery of 6% Alc. To identify Alc-heightened aggressors, each mouse was repeatedly tested for aggression after consuming either 1.0 g/kg Alc or H2O. Next, a cannula was implanted into either the DRN, OFC, or mPFC, and subsets of mice were tested for aggression after drinking either Alc or H2O prior to a microinjection of the 5-HT1B agonist, CP-94,253. Additional mice were implanted with a microdialysis probe into the mPFC, through which CP-94,253 was perfused and samples were collected for 5-HT measurement.
Approximately 60% of the mice were more aggressive after drinking Alc, confirming the aggression-heightening effects of 1.0 g/kg Alc. Infusion of 1 
g CP-94,253 into the DRN reduced both aggressive and motor behaviors.
However, infusion of 1 g CP-94,253 into the mPFC, but not the OFC, after Alc drinking, increased aggressive behavior. In the mPFC, reverse microdialysis of CP-94,253 increased extracellular levels of 5-HT; levels decreased immediately after the perfusion. This 5-HT increase was attenuated in self-administering mice.
These results suggest that 5-HT1B receptors in the mPFC may serve to selectively disinhibit aggressive behavior in mice with a history of Alc self-administration.
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