A schematic of summarized research investigating serotonergic circuits in the raphe nuclei, using chemogenetic manipulation. Cell-region specific manipulation; designed to manipulate region-dependent (MRN: median raphe, DRN: dorsal raphe) cell-type (5-HT: serotonergic neuron) specific activities (A-D). Output projection-cell specific manipulation; designed to modulate serotonergic projecting neurons to targeted regions (NAc; nucleus accumbens, OFC; orbitofrontal cortex, and CeA; central amygdala)(E-I). Input projection-cell specific manipulation; designed to manipulate specific projecting neurons (DA; dopaminergic, and glutamate; glutamatergic) from afferent regions (LHb; the lateral habenula, PAG; the periaqueductal gray) to the DRN (serotonergic) neurons (J-L).