LOCAL PHARMACOLOGICAL MANIPULATIONS OF PREFRONTAL DOPAMINE AFFECT CONFLICT BEHAVIOR IN RATS

Several lines of research have implicated the prefrontal cortex (PFC) and its dopaminergic (DA) innervation in an animal's response to stres s and anxiety. To extend these findings we evaluated the effects of bi lateral infusions of DA drugs into the medial PFC of rats, in a modifi ed conflict test, consisting of Reward, Conflict and Time-out componen ts. In experiment 1, the effects of infusions of the DA receptor agoni st apomorphine (APO) were compared to the effects of systemic injectio ns of the same drug. APO infusions induced a dose-dependent decrease o f responding in the Conflict component, indicative of an anxiogenic-li ke effect. However, response rates in the Reward component were simult aneously decreased, casting some doubt on the specificity of the effec t. In comparison, i.p injections of APO in a second group of animals d id not affect responding in the Conflict component, but dose-dependent ly decreased response rates during Time-out and Reward components. In experiment 2, we evaluated the effects of infusions of APO and the DA receptor antagonist cis-flupenthixol (FLU) into the medial PFC in the conflict test, and in one of its variants, the extinction of conflict test. Although both APO and FLU decreased response rates during Reward components, responding in the Conflict components of both tests was d ifferentially affected. APO infusions decreased Conflict responses, th e effect being more pronounced in the extinction of conflict test. In contrast, infusions of FLU increased responding in the Conflict compon ents. The respective pro- and anti-conflict effects of APO and FLU inf usions are In favour of a direct involvement of prefrontal DA in anxie ty-related behavioural responses.