Sellix Michael T, Egli Marcel, Henderson Ross P, Freeman Marc E
Department of Biological Science, Program in Neuroscience, Florida State University, Tallahassee, FL 32306, USA.
Brain Res. 2004 Apr 16;1005(1-2):164-81. doi: 10.1016/j.brainres.2004.01.049.
Dopamine (DA) is the primary inhibitor of prolactin (PRL) secretion. Three populations of neuroendocrine dopaminergic neurons (NDNs) designated tuberoinfundibular (TIDA), tuberohypophyseal (THDA) and periventricular hypophyseal DAergic (PHDA) neurons regulate PRL secretion. Given that ovarian steroids modulate both DA release and PRL secretion independently, we characterized the role of steroid hormones in coupling rhythmic NDN activity and PRL secretion. OVX rats under a standard 12:12 L:D cycle (L:D), constant dark (DD), or a 6-h phase-delayed L:D cycle (pdL:D) were treated with Estradiol-17beta (E) or E and Progesterone (E+P). NDN activity, defined by DA:DOPAC ratio in nerve terminals, was determined by HPLC-EC. E or E+P stimulated PRL surges in L:D that persisted under DD. In TIDA neurons, E or E+P treatment reduced the amount of DA released under L:D and DD and advanced the rhythm of DA turnover. E and E+P treatment reduced THDA and PHDA neuron activity under L:D, but did not affect these rhythms under DD. Circadian rhythms of PRL, corticosterone and DA turnover in NDN terminals from steroid treated rats entrained to a pdL:D cycle within 7 days. Therefore, ovarian steroids differentially adjust the timing and magnitude of NDN activity to facilitate coupling of DA release and PRL secretion.
多巴胺（DA）是催乳素（PRL）分泌的主要抑制剂。三类神经内分泌多巴胺能神经元（NDNs），即结节漏斗部（TIDA）、结节垂体部（THDA）和室周垂体多巴胺能（PHDA）神经元，调节PRL的分泌。鉴于卵巢甾体激素可独立调节DA释放和PRL分泌，我们研究了甾体激素在协调NDN节律性活动与PRL分泌中的作用。对处于标准12:12光暗周期（L:D）、持续黑暗（DD）或6小时相位延迟光暗周期（pdL:D）的去卵巢大鼠，给予17β-雌二醇（E）或E与孕酮（E+P）处理。通过高效液相色谱电化学检测法（HPLC-EC）测定神经末梢中DA与3,4-二羟基苯乙酸（DOPAC）的比值来定义NDN活性。E或E+P在L:D条件下刺激PRL分泌高峰，在DD条件下该高峰持续存在。在TIDA神经元中，E或E+P处理减少了L:D和DD条件下释放的DA量，并使DA周转节律提前。E和E+P处理在L:D条件下降低了THDA和PHDA神经元的活性，但在DD条件下不影响这些节律。经甾体激素处理的大鼠，其NDN末梢中PRL、皮质酮和DA周转的昼夜节律在7天内可适应pdL:D周期。因此，卵巢甾体激素以不同方式调节NDN活性的时间和幅度，以促进DA释放与PRL分泌的耦合。
