Schizophrenia (SCZ) is characterized by the aberrant development of the central nervous system and thereby results in impairments of multiple aspects of synaptic transmission, neuronal connectivity, and activity patterns. Dysfunctions of the dopaminergic circuitry were already postulated several decades ago. Patients with SCZ suffer from disturbances in the reward system, as well as in executive and cognitive functions. The two dopaminergic pathways, mesolimbic and mesocortical, have been implicated in neuropsychiatric disorders. Both originate from the ventral tegmental area and project to the nucleus accumbens and the prefrontal cortex, respectively.Here, we focus on the mesocortical pathway and present an in vitro co-culture model comprising glutamatergic and dopaminergic neurons, both of human origin, to study underlying disease mechanisms in SCZ.Our hiPSC-derived dopaminergic and glutamatergic neurons express subtype-specific synaptic markers and show robust single-cell activity in calcium imaging. GFP-labeling of glutamatergic neurons in our co-culture model allows for subtype-specific examinations of synapses and single-cell activity. Interestingly, we observed an overall reduction of presynaptic terminals and synapses. Furthermore, calcium imaging revealed significantly altered peak frequency for both neural types derived from patients.In conclusion, our humanized 2D in vitro model system allows us to study the reciprocal interaction of different neuronal cell types affected in SCZ. Moreover, we demonstrate the importance of closely recapitulating the in vivo situation by combining appropriate cell types into disease model systems. These systems can be further employed for the study of molecular mechanisms underlying neuropsychiatric diseases and may be helpful for future drug development.FKZ 35-4223.10-8