Discrete quinolinic acid lesions of the rat prelimbic medial prefrontal cortex affect cocaine- and MK-801-, but not morphine- and amphetamine-inducedreward and psychomotor activation as measured with the place preference conditioning paradigm

As a part of the mesocorticolimbic system, the medial prefrontal cortex (mP FC) is thought to participate in the regulation of locomotor activity, moti vation and reward. The mPFC consists of at least three different subareas. In previous lesion studies examining this region usually large parts of the mPFC were destroyed, with little discrimination between the different suba reas. Therefore, this study was designed to selectively lesion the prelimbi c area of the mPFC using a relatively low dose of quinolinic acid. In a con ditioned place preference (CPP) experiment, lesioned and control animals we re treated with cocaine (15 mg:kg), amphetamine (4 mg/kg), morphine (10 mg/ kg) or MK-801 (0.3 mg/kg) to induce CPP. The lesion blocked the development of CPP only in animals receiving cocaine, but not in animals receiving amp hetamine or morphine. MK-801 failed to produce a CPP in both lesioned and u nlesioned animals. During the conditioning experiment, the acute locomotor response to the different drugs was also measured. Only the response (in te rms of locomotion and rearing) to cocaine and MK-801 was reduced to a signi ficant extent by the lesion, while the response to amphetamine and morphine was not affected. Also, the lesions did not cause any changes in the spont aneous activity of the animals when tested without drug. These results show that even small lesions of the prelimbic subarea of the mPFC are sufficien t to produce behavioral effects. However, these are apparent only when the animals are challenged with cocaine or MK-801, but not with amphetamine or morphine, or when drug-free. This suggests that the mPFC might have a speci al role in mediating cocaine and MK-801 effects. (C) 1998 Elsevier Science B.V. All rights reserved.