Behavioral and mesocorticolimbic dopamine responses to non aggressive social interactions depend on previous social experiences and on the opponent'ssex

In these experiments we evaluated the relationship between behavioral and b rain dopamine (DA) responses to social interactions. Subjects were group ho used male mice confronted with a non aggressive male or female conspecific following either repeated defeat (defeated) or repeated non aggressive expe riences (social). Defeated mice showed more defensive/submissive reactions then mice of the social group regardless of the opponent sex. However, mice defeated by females showed reduced social exploration without significant differences in non social exploration whilst the opposite was true for mice defeated by male opponents. Non aggressive social interactions enhanced do pamine metabolism in the prefrontal cortex (pFC) of DEFEATED mice regardles s of opponent sex. However, only mice defeated by females showed enhanced d opamine metabolism and release in the nucleus accumbens septi (NAS) and olf actory tubercle (OT) following interaction with the non aggressive opponent . Finally, correlation between central and behavioral responses evidenced t hat 3,4-dihydroxiphenilacetic acid levels in the pFC were positively correl ated with defensive behaviors and negatively correlated with non social exp loration in mice confronted with male opponents but not in those confronted with females. The latter, showed a significant positive correlation betwee n 3-methoxytyramine (3-MT) levels in the OT and defensive responses and sig nificant negative correlation between social investigation and 3-MT levels in the OT and in the NAS. These results indicate a strict relationship betw een mesocorticolimbic dopamine transmission and behavior responses to socia l cues. Moreover, they strongly support the view that mesocorticolimbic DA modulates social behavior by affecting perceptive processing. (C) 2000 Else vier Science B.V. All rights reserved.