Infralimbic and dorsal raphé microinjection of the 5-HT(1B) receptor agonist CP-93,129: attenuation of aggressive behavior in CFW male mice.

RATIONALE

Aggressive behavior and impaired impulse control have been associated with dysregulations in the serotonergic system and with impaired functioning of the prefrontal cortex. 5-HT(1B) receptors have been shown to specifically modulate several types of offensive aggression.

OBJECTIVE

This study aims to characterize the relative importance of two populations of 5-HT(1B) receptors in the dorsal raphé nucleus (DRN) and infralimbic cortex (ILC) in the modulation of aggressive behavior.

METHODS

Male CFW mice were conditioned on a fixed-ratio 5 schedule of reinforcement to self-administer a 6% (w/v) alcohol solution. Mice repeatedly engaged in 5-min aggressive confrontations until aggressive behavior stabilized. Next, a cannula was implanted into either the DRN or the ILC. After recovery, mice were tested for aggression after self-administration of either 1.0 g/kg alcohol or water prior to a microinjection of the 5-HT(1B) agonist, CP-93,129 (0-1.0 μg/infusion).

RESULTS

In both the DRN and ILC, CP-93,129 reduced aggressive behaviors after both water and alcohol self-administration. Intra-raphé CP-93,129 dose-dependently reduced both aggressive and locomotor behaviors. However, the anti-aggressive effects of intra-cortical CP-93,129 were behaviorally specific.

CONCLUSIONS

These findings highlight the importance of the serotonergic system in the modulation of aggression and suggest that the behaviorally specific effects of 5-HT(1B) receptor agonists are regionally selective. 5-HT(1B) receptors in a medial subregion of the prefrontal cortex, the ILC, appear to be critically involved in the attenuation of species-typical levels of aggression.