The pigment-dispersing hormone causes the migration of the distal retinal pigment into the proximal end of the pigment chromatophore cells and thus decreases the amount of light entering the retinulas. May also function as a neurotransmitter and/or neuromodulator (By similarity). Expressed strongly in the head and weakly in the ventral nerve cord. Not detected in the midgut cecum or hindgut. In the cephalic neural complex, specifically localized to cells within the optic lobe, anteromedian protocerebrum, accessory lobe, tritocerebrum, and subesophageal ganglion. Belongs to the arthropod PDH family.