Goldstein Jeffrey, Hoff Karin, Hillyard Stanley D
Department of Biology and School of Dentistry, University of Nevada, 4505 Maryland Pkwy, Las Vegas, NV 89154-4004, USA.
Comp Biochem Physiol A Mol Integr Physiol. 2003 Nov;136(3):557-63. doi: 10.1016/s1095-6433(03)00205-8.
Toads (Bufo punctatus) use a sequence of two postures to place the ventral skin on a moist surface and absorb water osmotically. First, the skin contacts the surface (seat patch down, SPD), and then the hindlimbs are abducted to maximize skin contact area (water absorption response, WR). Toads modulated behavior in response to hydration status and osmotic content of the hydration source. Dehydrated toads placed on water displayed both SPD and WR. Hydrated toads injected with angiotensin II (AII) displayed SPD longer than Ringer-injected controls but did not initiate WR and absorbed less water than dehydrated toads. These results suggest that dehydration has a more robust dipsogenic effect than AII. Dehydrated toads placed on 250 mM NaCl briefly initiated SPD but not WR. The addition of amiloride to the hyperosmotic salt solution resulted in brief display of WR but no water loss. Hydrated toads placed on 250 mM NaCl showed shorter periods of SPD behavior. The combination of AII injection and amiloride addition to the salt solution increased SPD initiation but SPD duration was short and water loss was prevented. Neither AII nor dehydration overrides chemosensory mechanisms in the skin that suppress cutaneous drinking from hypertonic solutions.
蟾蜍（Bufo punctatus）通过一系列两个姿势将腹部皮肤置于潮湿表面，并通过渗透作用吸收水分。首先，皮肤接触表面（座位斑块向下，SPD），然后后肢外展以最大化皮肤接触面积（吸水反应，WR）。蟾蜍会根据水合状态和水合源的渗透压调节行为。置于水中的脱水蟾蜍会表现出SPD和WR。注射血管紧张素II（AII）的水合蟾蜍表现出SPD的时间比注射林格氏液的对照组长，但没有引发WR，且吸收的水分比脱水蟾蜍少。这些结果表明，脱水比AII具有更强的致渴作用。置于250 mM NaCl溶液中的脱水蟾蜍短暂地引发了SPD，但没有引发WR。在高渗盐溶液中加入氨氯吡咪导致短暂出现WR，但没有水分流失。置于250 mM NaCl溶液中的水合蟾蜍表现出SPD行为的时间较短。在盐溶液中注射AII并加入氨氯吡咪的组合增加了SPD的引发，但SPD持续时间较短且防止了水分流失。AII和脱水都不会超越皮肤中的化学感应机制，该机制会抑制从高渗溶液中进行皮肤饮水。
