Dopaminergic inputs to the prefrontal cortex are important for the integration of neuronal signals, the formation of working memory, and the establishment of memory fields. A detailed characterization of cellular mechanisms underlying dopamine effects on neurons in prefrontal cortex is emerging. An important issue is dopamine's net effect on excitability in local neuronal networks and its ability to modify epileptiform activity. In this article, dopamine's effects on single cells and local neuronal networks in vitro are reviewed. Our results from whole cell recording and voltage-sensitive dye imaging show that dopamine's net effect is to increase inhibition. Acting via D1-like receptors, dopamine restricts spatiotemporal spread of synaptic activity in local neocortical networks, predictive of a suppressive effect on epileptiform activity. Emerging technologies should allow examination of effects of dopamine receptor activation in vivo and allow clarification of dopamine's role in epilepsy.