Fig. 5

A Schematic of SNc dopamine (DA) and DRN serotonin (5HT) innervation of the hippocampus, and the effects of L-DOPA. The model was previously developed in (Reed et al. 2012) and extended here by adding the stimulation of the DRN by the SNc. It is the decrease of this stimulation, as SNc cells die, that causes the decline of serotonin in the hippocampus. B Simulation of relative concentrations of serotonin and dopamine in the hippocampus depends on the fractions of surviving SNc cells. C The course of extracellular dopamine in the hippocampus after a L-DOPA dose and its dependence on the fraction of SNc cells alive. D Simulation of hippocampal extracellular serotonin upon administration of Escit 60 min after the start of the simulation (see “Methods and Materials”). The MPTP trace (red) is computed by reducing the fraction of SNc cells alive to 0.35(Reed et al. 2012)