Tagawa R, Takahara J, Sato M, Niimi M, Murao K, Ishida T
First Department of Internal Medicine, Kagawa Medical School, Japan.
Life Sci. 1992;51(10):727-32. doi: 10.1016/0024-3205(92)90481-4.
Dopamine (DA) has dual actions (inhibitory and stimulatory) in the regulation of prolactin (PRL) release, depending on its concentration. To investigate the stimulatory effects of DA, perifused rat anterior pituitary cells were exposed to the highly-specific DA D2 receptor agonist, quinpirole hydrochloride (LY). Very low concentrations of LY (10(-12)-10(-10) M) stimulated PRL release and potentiated thyrotropin-releasing hormone (TRH)-induced PRL release. Higher concentrations of LY did not stimulate. Pretreatment with pertussis toxin (30 ng/ml, 24 h) completely abolished these effects of LY. The D2 receptor antagonist, metoclopramide, also blocked the potentiation by LY of TRH-induced PRL release. These data indicate that very low concentrations of dopamine stimulate PRL release via an interaction with a D2 receptor connected to a pertussis toxin-sensitive G protein.
多巴胺（DA）在调节催乳素（PRL）释放方面具有双重作用（抑制和刺激），这取决于其浓度。为了研究DA的刺激作用，将经灌流的大鼠垂体前叶细胞暴露于高度特异性的DA D2受体激动剂盐酸喹吡罗（LY）。极低浓度的LY（10^(-12)-10^(-10) M）刺激PRL释放，并增强促甲状腺激素释放激素（TRH）诱导的PRL释放。较高浓度的LY则无刺激作用。用百日咳毒素（30 ng/ml，24小时）预处理可完全消除LY的这些作用。D2受体拮抗剂甲氧氯普胺也可阻断LY对TRH诱导的PRL释放的增强作用。这些数据表明，极低浓度的多巴胺通过与连接到对百日咳毒素敏感的G蛋白的D2受体相互作用来刺激PRL释放。
