EFFECTS OF DOPAMINERGIC AND GLUTAMATERGIC RECEPTOR ANTAGONISTS ON THEACQUISITION AND EXPRESSION OF COCAINE CONDITIONING PLACE PREFERENCE

A balanced conditioning place preference (CPP) paradigm was used to st udy the role of dopamine D-1 and D-2 and glutamatergic NMDA and AMPA/k ainate receptors on the acquisition and expression of cocaine place co nditioning. The D-1 receptor antagonist SCH 23390 (0.1-0.2 mg/kg i.p.) , administered before cocaine during the training phase, significantly blocked the establishment of place conditioning (acquisition) but had no effect when administered before testing for place preference in th e absence of cocaine (expression). Similar results were obtained with the non-competitive NMDA receptor antagonist MK-801 (0.1-0.5 mg/kg i.p .). The D-2 receptor antagonist(-)-sulpiride (50-100 mg/kg i.p.) had n o effect on either acquisition or expression of cocaine CPP. The AMPA/ kainate receptor antagonist DNQX, administered intracerebroventricular ly (0.2-3 mu g/10 mu l), blocked cocaine CPP when given before testing but not when given before cocaine during the training trials. The res ults suggest that dopaminergic D-1 (but not D-2) and glutamatergic NMD A receptors are involved in the primary rewarding properties of cocain e (as assessed by the establishment of CPP) whereas the AMPA/kainate r eceptors are important only for the behaviour elicited by the stimuli previously associated with the drug action (CPP expression). The impli cations for the treatment of cocaine craving and relapse are discussed .