Neural mechanism for initiation of labor and maternal behavior

从我们之前的结果可知，一氧化氮（NO）给予脑室抑制分娩和母性行为在怀孕后期的大鼠。本项目从重新检查先前实验脑切片中NADPH diaphorase组织化学估计的NO活性开始。我们发现，与脑垂体后叶相反，脑垂体前叶的NO活性在分娩时被激活（NeuroReport 8: 817-821, 1997）。然后用免疫组织化学和NADPH降脂酶组织化学检测同种组织中NO合酶的变化。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。这一结果提示脑垂体前叶NO可能参与了对进入该腺体的血流量的控制（Brain Research 784: 337-340, 1997）。为了了解一氧化氮在中枢神经系统中对母性行为的调控作用，将一氧化氮供体注入哺乳期大鼠侧脑室。正如我们之前报道的那样，这些大鼠的泌乳反射受到抑制，室旁核、视上核和弓形正中隆起的Fos表达受到抑制。这些结果表明，一氧化氮调节这些核中的神经元的活动，从而影响垂体前叶激素，而垂体前叶激素参与控制这些激素的分泌和分娩的开始（NeuroReport and Brain Research, in press）。我们希望开发一种评估下丘脑各核NO表达的新方法。

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.