Like dopamine, dopamine agonists (bromocriptine, quinagolide and cabergolin) inhibit the release of PRL and GH. Dopamine agonists specifically bind to the D2-dopaminereceptor. Via signal transduction the secretion of vesicles with hormones is inhibited.
Although dopamine agonists in theory inhibit the release of most anterior pituitary hormones, their use is restricted to hypersecretion of PRL and GH. The most important use of dopamine agonists is to treat hyperprolactinemia caused by prolactinomas.
Dopamine agonists do NOT inhibit lactation.
Extra info: Dopamine agonists (like dopamine) inhibit lactation because they inhibit the release of PRL in the pituitary. They are also used to stop postnatal lactation.