DRD2 and pituitary gland adenoma: In this review we summarize data on angiogenesis in human pituitary adenomas, as well as in two mouse models of dopamine agonist resistant prolactinomas: the dopamine D2 receptor (D2R) knockout mouse (Drd2−/−) [9] and the lactotrope specific D2R knockout mouse (lacD2RKO) generated by Cre LoxP technology [10].