Reproductive experience and expression of dopamine D2 receptor mRNA:: A possible mechanism for reduced prolactin secretion in primiparous rats
Reproductive experience and expression of dopamine D2 receptor mRNA:: A possible mechanism for reduced prolactin secretion in primiparous rats
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DOI：
10.1111/j.1365-2826.2007.01586.x
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发表时间：
2007-10-01
影响因子：
3.2
通讯作者：
Bridges, R. S.
中科院分区：
文献类型：
--
作者：
Byrnes, E. M.;Bridges, R. S.
生殖经验（即妊娠和哺乳）导致女性和大鼠的循环催乳素水平降低。多巴胺拮抗剂对催乳素分泌的刺激在两个物种的生殖经验后也减弱。尽管在卵巢切除大鼠中，氟哌啶醇刺激的催乳素分泌明显减少，但尚不清楚在有生殖经验的周期性发情期大鼠中是否存在类似的催乳素分泌衰减。本研究探讨了这种可能性。此外，要确定可能的机制参与奇偶介导的催乳素分泌的变化，无论是多巴胺利用弓状核/正中隆起和多巴胺D-2受体mRNA的表达（短和长的形式）在垂体前叶整个下午的发情期在生殖经验和经验不足的女性。催乳素分泌较低的下午催情期的女性相比，年龄匹配，未经产的控制。此外，氟哌啶醇刺激的催乳素分泌减少卵巢切除，生殖经验丰富的女性。虽然没有观察到多巴胺利用率的差异作为一个功能的生殖经验，奇偶性确实影响两种形式的D-2受体mRNA在垂体前叶的表达。与未经产对照组相比，经产雌性在发情前期12.00 h时D-2长mRNA表达增加，在发情前期14.00 h时D-2短mRNA表达增加。由于D-2长/D-2短的比例可以显着影响催乳细胞的增殖和催乳素分泌，在两个D-2受体亚型的相对表达的转变，在垂体前叶的经产女性可能有助于解释减少催乳素分泌，发生以下生殖经验。
Reproductive experience (i.e. pregnancy and lactation) leads to reduced levels of circulating prolactin in both women and rats. Stimulation of prolactin secretion by dopamine antagonists is also blunted following reproductive experience in both species. Whereas a parity-induced reduction in haloperidol-stimulated prolactin secretion is evident in ovariectomised rats, it is unknown whether a similar attenuation of prolactin secretion is present in reproductively experienced, cycling pro-oestrous rats. The present study examined this possibility. Moreover, to determine possible mechanisms involved in parity-mediated changes in prolactin secretion, both dopamine utilisation within the arcuate nucleus/median eminence and expression of dopamine D-2 receptor mRNA (short and long forms) in the anterior pituitary were measured across the afternoon of pro-oestrous in reproductively experience and inexperienced females. Prolactin secretion was lower on the afternoon of pro-oestrous in primiparous females compared to age-matched, nulliparous controls. In addition, haloperidol-stimulated prolactin secretion was reduced in ovariectomised, reproductively experienced females. Although no differences in dopamine utilisation were observed as a function of reproductive experience, parity did affect the expression of both forms of D-2 receptor mRNA in the anterior pituitary. Compared with nulliparous controls, primiparous females had increased D-2 long mRNA expression at 12.00 h on pro-oestrous as well as increased D-2 short mRNA expression at 14.00 h. Because the ratio of D-2 long/D-2 short can significantly effect lactotroph proliferation and prolactin secretion, a shift in relative expression of the two D-2 receptor isoforms within the anterior pituitary of parous females may help account for the reduction in prolactin secretion that occurs following reproductive experience.