Neural mechanism for initiation of labor and maternal behavior

从我们以前的研究结果，我们知道，一氧化氮（NO）给药到脑室抑制分娩和母亲的行为在晚期妊娠大鼠。本研究以先前实验的脑切片中的NADPH黄递酶组织化学评估的NO活性为起点。我们发现，与垂体后叶相反，在分娩期间，垂体前叶中的NO活性被激活（NeuroReport 8：817-821，1997）。然后在同一组织标本中用荧光化学法和NADPH黄递酶组织化学法检测NO合酶。我们发现一些表达NO合酶的垂体前叶细胞位于与毛细血管接触的位置。这一结果表明，垂体前叶中的NO可能参与控制流入该腺的血流（Brain Research 784：337-340，1997）。为了解NO在中枢神经系统中控制母性行为的作用，将NO供体注入哺乳期大鼠侧脑室。如我们以前报道的，这些大鼠的排乳反射被抑制，室旁核、视上核和延髓正中隆起的Fos表达被抑制。这些结果表明，NO调节这些核中神经元的活性，以影响参与控制这些激素分泌和分娩启动的垂体前叶激素（NeuroReport和Brain Research，出版中）。我们希望继续这个项目，开发一种新的方法来评估NO在下丘脑每个核团的表达。

From our previous results it is known that nitric oxide (NO) given into the cerebroventricle inhibits delivery and maternal behavior in late pregnant rats. This project has started with reexamining NO activity estimated by NADPH diaphorase histochemistry in the brain slices of the previous experiment. We found that contrary to the posterior pituitary gland , NO activity in the anterior pituitary gland is activated during the time of parturition (NeuroReport 8 : 817-821, 1997). Then we examined NO synthase by immunohistochemistiy and NADPH diaphorase histochemistry in the same tissue preparation. We found that some anterior pituitary cells which express NO synthase locate in contact with capillaries. This result indicates that NO in the anterior pituitary gland may be involved in the control of blood flow into the gland (Brain Research 784 : 337-340, 1997). In order to know the role of NO in the central nervous system to control maternal behavior, NO donor was injected into the lateral ventricle of lactating rats. As we had previously reported, milk-ejection reflex was inhibited in these rats and Fos expression in the paraventricular nucleus, supraoptic nucleus and arcuate-median eminence was suppressed. These results suggest that NO regulates activity of neurons in these nuclei to influence anterior pituitary hormones that are involved in controlling these hormonal secretion and initiation of parturition (NeuroReport and Brain Research, in press). We want to pursue the project to develop a new method to evaluate NO expression in each nucleus of the hypothalamus.