The medial prefrontal cortex as a part of the brain reward system

This review will briefly summarize experimental evidence for an involvement of the medial prefrontal cortex (mPFC) in reward-related mechanisms in the rat brain. The mPFC is part of the mesocorticolimbic dopaminergic system. It receives prominent dopaminergic input from the ventral tegmental area (V TA) and, via the mediodorsal thalamus, inputs from other subcortical basal ganglia structures. In turn it projects back to the VTA and the nucleus acc umbens septi (NAS), which are generally considered as main components of th e brain reward system. Evidence for the involvement of the mPFC in reward-related mechanisms comes mainly from three types of studies, conditioned place preference (CPP), in tracranial self-stimulation (ICSS), and self-administration. Work will be s ummarized that has shown that certain drugs injected into the mPFC can prod uce CPP or that lesions of the mPFC can disrupt the development of CPP, tha t ICSS is obtained with the stimulating electrode placed in the mPFC, and t hat certain drugs are self-administered into the mPFC or that lesions of th e mPFC disrupt the peripheral self-administration of certain drugs. However, it has also been shown that the role of the mPFC in reward is not uniform. For example, the mPFC appears to be particularly important for the rewarding actions of cocaine, while it appears not to be important for the rewarding actions of amphetamine. Also, different subareas of the mPFC app ear to be differentially involved in the rewarding actions of different dru gs. Taken together, the available evidence shows that some drugs can produce re ward directly within the mPFC, and that some drugs, even though not having direct rewarding effects within the mPFC, depend on the function of the mPF C for the mediation of their rewarding effects.