Thomas A, Kim N B, Amico J A
Department of Medicine, University of Pittsburgh School of Medicine, Pennsylvania, USA.
J Neuroendocrinol. 1996 Oct;8(10):793-800. doi: 10.1046/j.1365-2826.1996.52210.x.
The hypothalamic peptides arginine vasopressin (AVP) and oxytocin (OT) have been implicated as mediators of socio-sexual behaviors in addition to their roles in osmolar homeostasis (AVP), milk ejection and uterine contractility (OT). Within 24 h of parturition, OT and AVP messenger ribonucleic acid (mRNA) levels increase in the hypothalamic paraventricular, and to a lesser degree, the supraoptic nucleus (PVN and SON) of the rat. We previously reported that the prepartum increase in OT mRNA is related to the spontaneous decline in progesterone levels prior to parturition. We also reported that increases in PVN and SON OT mRNA can be induced by exposing the ovariectomized rat to a steroid regimen that mimics the steroid milieu of pregnancy, namely sequential estrogen and progesterone and subsequent progesterone withdrawal. Levels of PVN and SON AVP mRNAs were not affected by progesterone withdrawal in late pregnant rats or the steroid regimen that increased OT mRNA in ovariectomized rats. These observations suggest that other factors, perhaps hormonal, may influence AVP mRNA levels. A decline in testosterone coincident with waning progesterone levels also occurs prepartum. Since peak levels of AVP mRNA prepartum coincide with the prepartum decline in testosterone, we questioned whether declining testosterone levels are important for the increase in AVP mRNA levels. To examine a possible role for testosterone in the increased level of AVP mRNA in late pregnancy, we sequentially administered estradiol and testosterone long-term (2 weeks) and removed testosterone 48 h prior to sacrifice. This steroid regimen mimics the estrogen and testosterone pattern of late pregnancy in rats. AVP, but not OT, mRNA levels increased significantly in the PVN of ovariectomized rats receiving this steroid regimen. We also found that implantation of late pregnant rats with testosterone capsules to prevent the spontaneous prepartum decline in testosterone, attenuates the increase in PVN AVP, but not OT, mRNA on day 21 of pregnancy. The data show that sequential estrogen and testosterone and testosterone withdrawal increase the level of PVN AVP mRNA in the female rat.
下丘脑肽精氨酸加压素（AVP）和催产素（OT），除了在渗透压稳态（AVP）、射乳和子宫收缩（OT）中发挥作用外，还被认为是社会性行为的介质。在分娩后24小时内，OT和AVP信使核糖核酸（mRNA）水平在大鼠下丘脑室旁核以及程度较轻的视上核（PVN和SON）中升高。我们之前报道过，分娩前OT mRNA的增加与分娩前孕酮水平的自发下降有关。我们还报道过，通过使去卵巢大鼠接受模拟孕期激素环境的激素方案，即序贯给予雌激素和孕酮，随后撤去孕酮，可诱导PVN和SON中OT mRNA增加。晚孕大鼠撤去孕酮或使去卵巢大鼠OT mRNA增加的激素方案，均不影响PVN和SON中AVP mRNA的水平。这些观察结果表明，其他因素，可能是激素因素，可能会影响AVP mRNA水平。分娩前还会出现睾酮水平随孕酮水平下降而下降的情况。由于分娩前AVP mRNA的峰值水平与分娩前睾酮水平的下降同时出现，我们推测睾酮水平下降对AVP mRNA水平的升高是否重要。为了研究睾酮在晚孕期AVP mRNA水平升高中可能发挥的作用，我们长期（2周）序贯给予雌二醇和睾酮，并在处死前48小时去除睾酮。这种激素方案模拟了大鼠晚孕期的雌激素和睾酮模式。接受这种激素方案的去卵巢大鼠的PVN中，AVP而非OT的mRNA水平显著升高。我们还发现，给晚孕大鼠植入睾酮胶囊以防止分娩前睾酮的自发下降，会减弱妊娠第21天PVN中AVP而非OT的mRNA的增加。数据表明，序贯给予雌激素和睾酮以及撤去睾酮会增加雌性大鼠PVN中AVP mRNA的水平。
