dopamine and prolactin are inversely related

An increase of dopamine decreases prolactin only in the brain ie hypothalamus. Dopamine cannot cross the blood brain barrier. In the peripheral nervous system, dopamine behaves like a catecholamine drug. Hence the use a domperidone, a dopamine blocker, to not only suppress nausea and vomitting (via peripheral dopamine blocking) but must also lower dopamine in the CNS w/c would up prolactin=> lactation. Bromocriptine, a dopamine agonist is used to stop lactation. Breastfeeding increases prolactin, thus decreasing dopamine, and deductively should ahve something to do with postpartum depression.