D-1 DOPAMINE-RECEPTOR MEDIATION OF SOCIAL AND NONSOCIAL EMOTIONAL REACTIVITY IN MICE - EFFECTS OF HOUSING AND STRAIN DIFFERENCE IN MOTOR-ACTIVITY

The study examined the effects of isolation housing and the role of D- 1 dopamine receptors on isolation-induced social and nonsocial (acoust ic startle) reactivity in mice high (C57BL/6) and low (A) in motor act ivity. Isolation housing had no effect on acoustic startle but increas ed strain-specific forms of social reactivity. The D-1 agonist dihydre xidine (DHX) increased acoustic startle in isolated mice of both strai ns, but this: effect was more pronounced in C57BL/6 mice. In this stra in, DHX and the D-1 agonist SKF-81297 increased locomotor forms of soc ial reactivity (e.g., escape, jump), whereas the D-1 antagonist SCH-23 390 increased stationary reactivity (e.g., freezing). In A mice, DHX a nd SKF-81297 increased and decreased stationary reactivity, respective ly, whereas SCH-23390 had no effect on these behaviors. Administration of SKF-81297 after pretreatment with SCH-23390 or the D-2 antagonist sulpiride confirmed the importance of D-1 receptors in mediating speci fic forms of social reactivity in C57BL/6 mice. These results suggest an important relationship between social reactivity and motor activity and an important, albeit strain-dependent, role for D-1 receptors in mediating specific emotional behaviors.