Stricker Edward M, Hoffmann Myriam L
Department of Neuroscience, University of Pittsburgh, Pittsburgh, PA 15260, United States.
Physiol Behav. 2007 Jul 24;91(4):404-12. doi: 10.1016/j.physbeh.2007.04.007. Epub 2007 Apr 12.
Presystemic signals play an important role in the control of ingestive behavior by allowing animals to anticipate imminent physiological changes. The significance of such signals in the control of food intake has been amply demonstrated and is widely appreciated. Our recent experiments have revealed that presystemic signals also provide important early feedback when rats drink water or NaCl solution, before the ingested fluids are absorbed and influence cerebral osmoreceptors or cardiovascular baroreceptors. These early signals clearly affect vasopressin (VP) secretion and thirst. They relate either to the distension of the stomach and proximal small intestine (presumably mediated by local stretch receptors) or to the concentration of fluid that empties from the stomach into the small intestine (presumably mediated by visceral osmo- or Na(+)-receptors). Dehydrated dogs use functionally comparable signals from the oropharynx while drinking in order to inhibit both VP secretion and thirst. However, that system differs in several respects from the system in rats aside from the fact that the presystemic signals in rats are not oropharyngeal: in rodents, (a) separate early signals influence VP secretion and thirst, (b) early signals can provide both stimulation and inhibition of VP secretion and thirst, and (c) the early signals are associated with both the volume and concentration of ingested fluid. These presystemic signals also inhibit the intake of NaCl solution by rats with salt appetite.
摄食前信号在控制摄食行为中发挥着重要作用，它使动物能够预测即将发生的生理变化。此类信号在控制食物摄入方面的重要性已得到充分证明，并且得到广泛认可。我们最近的实验表明，在大鼠饮水或摄入氯化钠溶液时，摄食前信号在摄入的液体被吸收并影响脑渗透压感受器或心血管压力感受器之前，也能提供重要的早期反馈。这些早期信号明显影响血管加压素（VP）的分泌和口渴感。它们要么与胃和小肠近端的扩张有关（可能由局部牵张感受器介导），要么与从胃排空到小肠的液体浓度有关（可能由内脏渗透压或钠受体介导）。脱水的狗在饮水时利用来自口咽的功能类似的信号来抑制VP分泌和口渴感。然而，除了大鼠的摄食前信号不是来自口咽这一事实外，该系统在几个方面与大鼠的系统不同：在啮齿动物中，（a）不同的早期信号影响VP分泌和口渴感，（b）早期信号既能刺激也能抑制VP分泌和口渴感，（c）早期信号与摄入液体的体积和浓度都有关。这些摄食前信号还会抑制有盐食欲的大鼠对氯化钠溶液的摄入。
