Dopamine D2L receptor- and age-related reduction in offensive aggression.

The dopamine D2 receptor (D2) has been implicated in attention-deficit hyperactive disorder (ADHD) and aging. Two isoforms of D2 have been identified, termed D2L (long form) and D2S (short form). In this study, we investigated the role of D2L in offensive aggression, using mice lacking the dopamine D2L receptor (D2L-/-) as a model system and the resident-intruder test. We found that D2L-/- mice showed much lower levels of aggression than wild-type mice. Interestingly, offensive aggression also decreased as the age of the mice increased. These results suggest that both the D2L receptor and aging play roles in the modulation of offensive aggression. This finding may contribute to our understanding of the neurobiological basis of aggression.