麦芽4个化学部位通过多巴胺D2受体对产后缺乳模型大鼠催乳作用研究

目的基于多巴胺D2受体(DRD2),考察小剂量麦芽4个化学部位的催乳作用,初步探讨小剂量麦芽生物碱对产后缺乳模型大鼠泌乳素(PRL)分泌的调节机制。方法采用ig甲磺酸溴隐亭方法制备缺乳大鼠模型,造模成功后,各给药组均ig给予相应的药物,应用ELISA法检测各组大鼠血清PRL、雌二醇(E_2)、孕酮(P)水平;HE染色观察各组大鼠乳腺组织病理改变;采用实时荧光定量PCR(qRT-PCR)法检测各组大鼠脑垂体中泌乳素受体及DRD2 mRNA表达。结果与对照组比较,模型组大鼠血清中PRL、P及E_2水平、脑垂体PRL mRNA表达水平显著降低;脑垂体DRD2 mRNA表达水平显著升高。与模型组比较,麦芽总生物碱组大鼠乳腺小叶体积明显增加,导管明显扩张,且导管及腺泡内含有大量乳汁。麦芽总生物碱明显增加模型大鼠血清中PRL、P、E_2水平及脑垂体PRL mRNA表达水平,降低脑垂体DRD2 mRNA表达水平。结论麦芽催乳的主要药效物质为总生物碱,其作用机制可能与促进PRL分泌,增加脑垂体PRL受体、降低DRD2 mRNA表达水平有关。

Effects of lactagogue of four total alkaloids of barley malt via dopamine D2 receptor in postpartum hypogalactia rat

Objective To explore the regulatory effect of malt alkaloid on prolactin (PRL) secretion in the model rat with postpartum hypogalactia induced by bromocriptine based on dopamine D2 receptor, and determine the active fraction of the malt with galactogogue effect. Methods The postpartum hypogalactia model was established by intragastric administration of bromocriptine mesylate. After the model was successfully established, all groups were given corresponding drug treatment. The concentration of serum PRL, estradiol (E₂) and progesterone (P) in each group was detected by ELISA kits. HE staining was used to observe the pathologic changes of breast tissue. RT-PCR was used to determine the mRNA levels of prolactin receptor (PRLR) and dopamine D2 receptor (DRD2) in pituitary gland of rats. Results Compared with the control group, the levels of serum PRL, P, and E₂ were significantly decreased in the model group as well as the mRNA expression of the pituitary PRL cells. But the mRNA expression of the pituitary DRD2 in the model group was significantly increased compared with the control group. Compared with the model group, the malt total alkaloid significantly increased the volume of mammary lobule and dilated the duct. There was a lot of milk in the duct and acinar in the malt total alkaloid group. Besides, the total alkaloids increased the concentration of serum PRL, P, and E2 and the mRNA expression of the pituitary PRL cells, and decreased the mRNA expression of the pituitary DRD2. Conclusion The primary the active fraction of malt for galactogogue action is total alkaloids, and its mechanism may be related to promoting PRL secretion, increasing serum PRL receptor level and decreasing the mRNA expression of dopamine D2 receptor.