Higuchi T, Honda K, Takano S, Negoro H
Department of Physiology, Fukui Medical School, Japan.
J Endocrinol. 1988 Feb;116(2):225-30. doi: 10.1677/joe.0.1160225.
The release of oxytocin in response to an osmotic stimulus and immobilization stress was compared in lactating rats 8-12 days after delivery and in non-lactating rats. Intravenous injection of hypertonic saline or immobilization stress induced an increase in blood oxytocin levels in both lactating and non-lactating rats, but the increment in the former was significantly lower than that in the latter. The lower responsiveness of oxytocin release to stress in lactating rats was not altered by ovariectomy 2 days after parturition. Oxytocin release induced by electrical stimulation of the anteroventral third ventricle (an osmoreceptive area), paraventricular nucleus and neurohypophysis was significantly lower, to a similar extent, in lactating rats compared with non-lactating rats. These findings indicate that the structural reorganization reported in the hypothalamo-neurohypophysial system may not function to facilitate release of oxytocin in response to stress and osmotic stimulus in lactating rats. The reduced responsiveness of the release of oxytocin is independent of the influence of ovarian hormones, and may be due to the low ability of the oxytocin neurone itself to release oxytocin, and/or due to the activated inhibitory influence on the oxytocin neurone in the lactating rat.
在分娩后8 - 12天的泌乳大鼠和非泌乳大鼠中，比较了对渗透刺激和固定应激反应时催产素的释放情况。静脉注射高渗盐水或施加固定应激，均可使泌乳大鼠和非泌乳大鼠的血液催产素水平升高，但前者的增幅显著低于后者。产后2天进行卵巢切除，并未改变泌乳大鼠催产素释放对应激的较低反应性。与非泌乳大鼠相比，电刺激腹前第三脑室（一个渗透压感受区域）、室旁核和神经垂体所诱导的泌乳大鼠催产素释放，在相似程度上显著降低。这些发现表明，下丘脑 - 神经垂体系统中报道的结构重组，可能无法促进泌乳大鼠对应激和渗透刺激产生的催产素释放。催产素释放反应性降低与卵巢激素的影响无关，可能是由于催产素神经元自身释放催产素的能力较低，和/或由于泌乳大鼠对催产素神经元的抑制性影响被激活。
