Blair-West J R, Denton D A, McKinley M J, Weisinger R S
Howard Florey Institute of Experimental Physiology and Medicine, University of Melbourne, Parkville, Victoria, Australia.
Am J Physiol. 1989 Nov;257(5 Pt 2):R1212-8. doi: 10.1152/ajpregu.1989.257.5.R1212.
Cows having free access to water (hydrated) or deprived of water for 26.5 h (dehydrated) were infused for 3 h with angiotensin II or captopril solutions intravenously (iv) or intracerebroventricularly (icv) beginning 1 h before access to 0.3 M NaHCO3/NaCl solution for 2 h. The results agree with the results of the experiments with the same agents and doses in Na-deficient cows. Only iv infusion of angiotensin II stimulated Na appetite and only icv infusion of angiotensin II stimulated thirst. Therefore, barriers to the penetration of angiotensin II in the brain determined the particular site of action and elicited response. Dehydration did not stimulate Na appetite and, as shown previously, Na deficiency did not stimulate thirst, but both behaviors seem to be influenced by angiotensin-related mechanisms in the brain. The inability of iv angiotensin II to stimulate Na appetite in hydrated cows might be explained by the lack of a response caused by, and common to, Na deficiency and dehydration, e.g., upregulation of angiotensin II receptors, or reduced extracellular fluid volume.
自由饮水（水合状态）或禁水26.5小时（脱水状态）的奶牛，在开始饮用0.3M NaHCO₃/NaCl溶液2小时前1小时，通过静脉注射（iv）或脑室内注射（icv）给予血管紧张素II或卡托普利溶液，持续3小时。这些结果与在缺钠奶牛中使用相同药物和剂量的实验结果一致。只有静脉注射血管紧张素II刺激钠食欲，只有脑室内注射血管紧张素II刺激口渴。因此，血管紧张素II在脑中的渗透屏障决定了其特定作用部位并引发反应。脱水不刺激钠食欲，如先前所示，缺钠也不刺激口渴，但这两种行为似乎都受脑中与血管紧张素相关机制的影响。静脉注射血管紧张素II在水合状态的奶牛中无法刺激钠食欲，这可能是由于缺乏由缺钠和脱水共同引起的反应，例如血管紧张素II受体上调或细胞外液体积减少。
