Nicholson G, Greeley G H, Humm J, Youngblood W W, Kizer J S
Brain Res. 1980 May 26;190(2):447-57. doi: 10.1016/0006-8993(80)90287-5.
The purpose of this study was to examine the thesis that increasing concentrations of prolactin within the cerebrospinal fluid (CSF) increase the activity of dopaminergic terminals within the median eminence and that this increased dopaminergic activity is temporally associated with a suppression of endogenous prolactin secretion. To avoid difficulties encountered in performing catecholamine turnovers in the undisturbed rat, the measurement of tyrosine hydroxylase was validated as an index of dopaminergic activity within the median eminence. In the median eminence, but not the medial preoptic area, parallel increases in the activity of tyrosine hydroxylase and the turnover of dopamine (but not norepinephrine) occurred following hyperprolactinemia. Twenty-six hours but not 2.5 h after the subcutaneous administration of ovine prolactin, the activity of tyrosine hydroxylase was increased in the median eminence, and endogenous prolactin secretion was inhibited. During a 26 h continuous intracerebroventricular (icv) infusion (88 ng/h) of rat prolactin, there was a complete suppression of endogenous prolactin secretion. Twenty-six but not 2.5 h after the initiation of the icv infusion of prolactin, there was an increase in tyrosine hydroxylase activity in the median eminence. The results of these studies suggest that: (1) measurement of tyrosine hydroxylase activity within the median eminence is a useful index of the activity of dopaminergic terminals; (2) increasing concentrations of prolactin within the CSF suppressed prolactin secretion by the anterior pituitary; (3) this suppression of prolactin is accompanied by an increased activity of dopaminergic terminals within the median eminence; (4) those neural structures concerned with the regulation of prolactin secretion respond directly to prolactin itself; (5) the autoregulation by prolactin of its own secretion manifests a certain latency more characteristic of a tonic rather than a phasic inhibitory control; and finally, (6) dopaminergic terminals in the median eminence but not the preoptic area appear uniquely sensitive to prolactin.
脑脊液（CSF）中催乳素浓度的升高会增加正中隆起内多巴胺能终末的活性，且这种多巴胺能活性的增加在时间上与内源性催乳素分泌的抑制相关。为避免在未受干扰的大鼠中进行儿茶酚胺周转测量时遇到的困难，酪氨酸羟化酶的测量被确认为正中隆起内多巴胺能活性的指标。在正中隆起而非内侧视前区，高催乳素血症后酪氨酸羟化酶活性和多巴胺（而非去甲肾上腺素）周转呈平行增加。皮下注射羊催乳素26小时后而非2.5小时后，正中隆起内酪氨酸羟化酶活性增加，内源性催乳素分泌受到抑制。在持续26小时的脑室内（icv）输注（88 ng/h）大鼠催乳素期间，内源性催乳素分泌被完全抑制。在开始icv输注催乳素26小时后而非2.5小时后，正中隆起内酪氨酸羟化酶活性增加。这些研究结果表明：（1）正中隆起内酪氨酸羟化酶活性的测量是多巴胺能终末活性的有用指标；（2）脑脊液中催乳素浓度的升高抑制了垂体前叶的催乳素分泌；（3）催乳素的这种抑制伴随着正中隆起内多巴胺能终末活性的增加；（4）那些与催乳素分泌调节有关的神经结构直接对催乳素本身作出反应；（5）催乳素对其自身分泌的自动调节表现出一定的潜伏期，更具持续性而非阶段性抑制控制的特征；最后，（6）正中隆起而非视前区的多巴胺能终末似乎对催乳素具有独特的敏感性。
