Nobata Shigenori, Ando Masaaki, Takei Yoshio
Laboratory of Physiology, Atmosphere and Ocean Research Institute, University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8564, Japan.
Gen Comp Endocrinol. 2013 Oct 1;192:214-21. doi: 10.1016/j.ygcen.2013.05.009. Epub 2013 May 22.
Marine teleost fishes drink environmental seawater to compensate for osmotic water loss, and the amount of water intake is precisely regulated to prevent dehydration or hypernatremia. Unlike terrestrial animals in which thirst motivates a series of drinking behaviors, aquatic fishes can drink environmental water by reflex swallowing without searching for water. Hormones are key effectors for the regulation of drinking. In particular, angiotensin II and atrial natriuretic peptide are likely candidates for physiological regulators because of their potent dipsogenic and antidipsogenic activities, respectively. In the eel, these hormones act on the area postrema in the medulla oblongata, a circumventricular structure without blood-brain barrier, which then regulates the activity of the glossopharyngeal-vagal motor complex. These motor neurons in the hindbrain innervate the upper esophageal sphincter muscle and other swallowing-related muscles in the pharynx and esophagus for regulation of drinking. Thus, the neural circuitry for drinking in fishes appears to be confined within the hindbrain. This simple mechanism is much different from that of terrestrial animals in which thirst sensation is induced through hormonal actions on the subfornical organ and organum vasculosum of the lamina terminalis that are located in the forebrain. It seems that the neural and hormonal mechanism that regulates drinking behavior has evolved from fishes depending on the availability of water in their natural habitats.
海洋硬骨鱼通过饮用环境海水来补偿渗透失水，并且精确调节饮水量以防止脱水或高钠血症。与陆地动物不同，陆地动物的口渴会引发一系列饮水行为，而水生鱼类可以通过反射性吞咽饮用环境水，无需寻找水源。激素是调节饮水的关键效应器。特别是，血管紧张素II和心房利钠肽分别因其强大的致渴和抗致渴活性，可能是生理调节剂的候选者。在鳗鱼中，这些激素作用于延髓的最后区，这是一个没有血脑屏障的室周结构，然后调节舌咽-迷走运动复合体的活动。后脑的这些运动神经元支配食管上括约肌以及咽部和食管中其他与吞咽相关的肌肉，以调节饮水。因此，鱼类饮水的神经回路似乎局限于后脑。这种简单的机制与陆地动物的机制有很大不同，在陆地动物中，口渴感是通过激素作用于位于前脑的穹窿下器官和终板血管器而诱发的。调节饮水行为的神经和激素机制似乎是根据鱼类自然栖息地中水的可获得性从鱼类进化而来的。
