tokens: There was no change in the levels of DA , norepinephrine ( NE ) , serotonin ( 5 - HT ) , or their metabolites in the arcuate nucleus ( AN ) , medial preoptic area ( MPA ) , caudate putamen ( CP ) , substantia nigra ( SN ) , and zona incerta ( ZI ) , except for a decrease in 5 - hydroxyindoleacetic acid ( 5 - HIAA ) in the AN after 6 - months of hyperprolactinemia and an increase in DA concentrations in the AN after 9 - months of hyperprolactinemia .