Maeda T, Ikegami H, Sakata M, Yamaguchi M, Wada K, Koike K, Adachi K, Kurachi H, Hirota K, Miyake A
Department of Obstetrics and Gynecology, Osaka University Medical School, Japan.
J Endocrinol Invest. 1996 Oct;19(9):586-92. doi: 10.1007/BF03349022.
The effect of estradiol (E2) on rat tuberoinfundibular dopaminergic (TIDA) neurons was examined in vivo, employing chronic intraventricular (i.c.v.) infusion technique using an osmotic mini-pump. The activity of TIDA neurons was assessed by the release and synthesis of prolactin (PRL) in the rat pituitary gland and by the changes in the 3, 4-dihydroxyphenylacetic acid (DOPAC) and dopamine (DA) levels and in the DOPAC/DA ratio in the rat hypothalamus. We also examined the [3H] E2 binding in the rat hypothalamus. Ovariectomized female Wistar rats with E2 replacement were treated with daily i.c.v. infusion of 1 microM of E2 or saline vehicle for 1, 3, and 7 days using the Alzet osmotic mini-pump and brain infusion kit. At 1 day of i.c.v. infusion of E2, the serum PRL level was significantly decreased compared with that in the vehicle group. Northern blot analysis of the total RNA isolated from the pituitary glands demonstrated a decrease in the PRL gene transcript level in the E2 group. At 3 days of E2 treatment, however, the serum PRL level was significantly increased compared with that of the vehicle-injected group and Northern blot analysis also demonstrated that the PRL gene transcript level was increased in the E2 group. At 7 days of E2 administration, there were no significant differences between the E2 and vehicle groups in either serum PRL or PRL gene transcript levels. There was a significant increase in the DOPAC/DA ratio after 1 day in the E2 group. However, no significant effects of E2 on this ratio were observed at 3 and 7 days of treatment. The DOPAC concentration in the E2 group was significantly increased at day 1 and significantly decreased at day 3, compared with that of the respective time in vehicle group. At day 7 there was no significant change in DOPAC concentration in either groups. The DA concentrations in the hypothalamus was not changed on any day in either group. Specific [3H] E2 binding was observed in the rat hypothalamus. These data suggest that E2 may have a biphasic effect on the accumulation of PRL gene transcripts and on the PRL secretion in the rat pituitary by first stimulating and then inhibiting the TIDA neuronal activity.
采用渗透微型泵经脑室（i.c.v.）慢性输注技术，在体内研究了雌二醇（E2）对大鼠结节漏斗多巴胺能（TIDA）神经元的影响。通过大鼠垂体中催乳素（PRL）的释放和合成，以及大鼠下丘脑3,4 - 二羟基苯乙酸（DOPAC）、多巴胺（DA）水平和DOPAC/DA比值的变化，评估TIDA神经元的活性。我们还检测了大鼠下丘脑中[3H] E2的结合情况。用Alzet渗透微型泵和脑内输注套件，对去卵巢并用E2替代的雌性Wistar大鼠，每日经脑室输注1 μM E2或生理盐水载体，持续1、3和7天。在经脑室输注E2 1天时，与载体组相比，血清PRL水平显著降低。对从垂体分离的总RNA进行Northern印迹分析表明，E2组中PRL基因转录水平降低。然而，在E2处理3天时，与注射载体组相比，血清PRL水平显著升高，Northern印迹分析也表明E2组中PRL基因转录水平升高。在给予E2 7天时，E2组和载体组在血清PRL或PRL基因转录水平上均无显著差异。E2组在1天后DOPAC/DA比值显著升高。然而，在处理3天和7天时，未观察到E2对该比值有显著影响。与载体组相应时间相比，E2组中DOPAC浓度在第1天显著升高，在第3天显著降低。在第7天，两组中DOPAC浓度均无显著变化。两组中下丘脑DA浓度在任何一天均未改变。在大鼠下丘脑中观察到特异性[3H] E2结合。这些数据表明，E2可能通过首先刺激然后抑制TIDA神经元活性，对大鼠垂体中PRL基因转录本的积累和PRL分泌产生双相作用。
