Rasmussen D D, Jakubowski M, Allen D L, Roberts J L
Department of Reproductive Medicine, University of California, San Diego, La Jolla 92093-0802.
Neuroendocrinology. 1992 Sep;56(3):285-94. doi: 10.1159/000126241.
We have investigated putative dopaminergic regulation of opiomelanotropinergic activity in the arcuate/periarcuate mediobasohypothalamus (MBH) by assessing the changes in MBH tyrosine hydroxylase (TH; rate-limiting enzyme in catecholamine synthesis) and proopiomelanocortin (POMC; opiomelanotropin precursor) mRNA levels under conditions in which endogenous tuberinfundibular dopaminergic activity exhibits marked changes. Adult Sprague-Dawley rats were sacrificed at 09.00 and 15.00 h, and individual MBH POMC and TH cytoplasmic mRNA levels were simultaneously quantified by multiplex solution hybridization-RNase protection assay with protected fragments separated by polyacrylamide gel electrophoresis. In ovariectomized (OVX) rats treated for 3 days with low-dose estradiol (E2) implants (resulting in 18 +/- 4 pg E2/ml serum), the MBH levels of POMC and TH mRNAs were approximately 17 and 31% lower than those measured in OVX controls, respectively. In OVX rats implanted for 20 days with larger E2 implants (99 +/- 9 pg E2/ml serum), POMC and TH mRNA levels were approximately 29 and 41% lower than in OVX controls, respectively. Additional groups were exposed to the higher E2 dose for 20 days and then killed 10 or 20 days after removal of the E2 implant. In these rats, POMC mRNA levels rebounded to the same level seen in OVX controls, while TH mRNA levels even exceeded control values by 22-27%. TH and POMC mRNA levels did not change significantly between 09.00 and 15.00 h, except 10 days after removal of the E2 implants, when 09.00 h POMC mRNA levels were higher than the 15.00 h levels. MBH POMC and TH mRNA levels were positively correlated with each other within individual animals. This correlation is maintained when both POMC and TH mRNA levels are suppressed in response to both 3-day low-dose and 20-day high-dose E2 treatment. However, although rat MBH opiomelanotropinergic and tuberoinfundibular dopaminergic mRNA biosynthesis thus appear to be positively correlated, the coregulation or functional interactions of these two neuronal systems remain to be determined.
我们通过评估在内源性结节漏斗多巴胺能活性发生显著变化的条件下，弓状/弓状周围中基底下丘脑（MBH）中酪氨酸羟化酶（TH；儿茶酚胺合成中的限速酶）和阿黑皮素原（POMC；阿片黑素细胞刺激素前体）mRNA水平的变化，研究了MBH中阿片黑素细胞刺激素能活性的假定多巴胺能调节。成年Sprague-Dawley大鼠于上午9点和下午3点处死，通过多重溶液杂交-核糖核酸酶保护试验同时定量单个MBH中POMC和TH细胞质mRNA水平，并用聚丙烯酰胺凝胶电泳分离受保护片段。在用低剂量雌二醇（E2）植入物处理3天的去卵巢（OVX）大鼠中（导致血清E2水平为18±4 pg/ml），MBH中POMC和TH mRNA水平分别比OVX对照组低约17%和31%。在用较大E2植入物植入20天的OVX大鼠中（血清E2水平为99±9 pg/ml），POMC和TH mRNA水平分别比OVX对照组低约29%和41%。另外几组大鼠接受高剂量E2处理20天，然后在移除E2植入物后10天或20天处死。在这些大鼠中，POMC mRNA水平回升至OVX对照组的水平，而TH mRNA水平甚至比对照值高出22%-27%。除了在移除E2植入物10天后，上午9点的POMC mRNA水平高于下午3点的水平外，上午9点和下午3点之间TH和POMC mRNA水平没有显著变化。在个体动物中，MBH中POMC和TH mRNA水平彼此呈正相关。当POMC和TH mRNA水平因3天低剂量和20天高剂量E2处理而均被抑制时，这种相关性仍然存在。然而，尽管大鼠MBH中阿片黑素细胞刺激素能和结节漏斗多巴胺能mRNA生物合成因此似乎呈正相关，但这两个神经元系统的共同调节或功能相互作用仍有待确定。
