Neurophysiological study on salt appetite in rats.

在动物体内，盐的食欲和口渴在体液平衡控制中起着重要作用，以维持等渗和等容。本研究的目的是阐明诱导大鼠盐食欲的可能的神经机制。关注的重点是肝门静脉外周渗透和后脑区（心室周围器官之一）的作用。肝门静脉渗透在肝门静脉区存在渗透受体机制。研究表明，来自肝门静脉渗透受体的传入脉冲主要在左侧孤束核（NTS）的尾侧部分投射，并在该核内被调节和整合。从NTS到下丘脑已经确认了三条不同的通路：(1)直接投射通路，(2)通过臂旁核的通路，这两条通路都可能参与盐的食欲或口渴。(3)一条经尾侧髓质腹外侧的通路，可能在调节ADH分泌中起作用。脑后区域内的钠（或渗透）反应神经元。后脑区（AP）是脑室周围器官之一，缺乏血脑屏障。有证据表明，钠（或渗透）反应神经元存在于Ap中，除了众所周知的化学感受器触发呕吐功能外，后脑渗透受体机制可能参与该结构。这表明，由于Ap和NTS之间的功能联系，Ap渗透接受可能有助于体液的稳态控制，其中外周渗透传入信号被投射并传递到下丘脑。

Salt appetite as well as thirst plays an important role on homeostatic control of body fluid to maintain isosmosis and isovolemia in animals. The purpose of this study is to elucidate possible neuronal mechanisms which induce salt appetite in rats. The attention has been directed to the roles of peripheral hepatoportal osmoreception and the area postrema, one of the circumventricular organs.1. Hepatoportal osmoreception There exists an osmoreceptor mechanism in the hepatoportal region. It has been clarified that afferent impulses from the hepatoportal osmoreceptors are projected within the caudal portion of the nucleus tractus solitarius (NTS) dominantly on left hand side and they are modulated and integrated inside this nucleus. Three different pathways have been confirmed from the NTS to the hypothalamus : (1) A direct projection pathway, (2) A pathway via the parabrachial nucleus, both pathways may participate in salt appetite or thirst. (3) A pathway via the caudal ventrolateral medulla, which may play a role on regulation of ADH secretion.2. Sodium (or osmo-) responsive neurons within the area postrema. The area postrema (AP) is one of the circumventricular organs and lacks the blood brain barrier. Evidence has been established that sodium (or osmo-) responsive neurons exist within the Ap and hindbrain osmoreceptor mechanism may be involved in this structure in addition to the well known chemoreceptor trigger function for vomitting. It suggests that the Ap osmoreception may contribute to the homeostatic control of body fluid due to functional linkage between the AP and the NTS where the peripheral osmotic afferent signal are projected, and transmitted to the hypothalamus.