l-dopa-induced dopamine synthesis and oxidative stress in serotonergic cells

► Dopamine can be produced within serotonergic neurons after l-dopa incubation. ► l-dopa incubation results in reactive oxygen species and toxicity in serotonergic neurons. ► Toxicity is dependent on l-dopa conversion to dopamine, and dopamine metabolism by MAO. ► Co-treatment of l-dopa with an MAO inhibitor blocks ROS and toxicity in serotonergic neurons.