Impaired drinking responses of rats with lesions of the subfornical organ.

Electrolytic lesions of the subfornical organ (SFO) in rats are known to abolish their drinking response to iv infusion of angiotensin II (AII). Such lesions also attenuate drinking after 20% polyethylene glycol solution (PEG) is given sc, which suggests that AII may play an important role in mediating thirst during hypovolemia. However, the 3 present studies show that male albino Sprague-Dawley rats (N?=?57) with SFO lesions drank normal amounts when larger plasma volume deficits were caused by 30% PEG treatment. Ss did not drink in response to relatively low doses of hypertonic saline but drank normal amounts when given larger doses. Results suggest that the SFO is involved in a control system for thirst and that after damage to it, greater stimulation than usual may be required for drinking to be initiated. From this perspective, drinking would be expected following either suprathreshold stimulation or drug-induced lowering of the activation threshold in these animals, as was observed, with the loss of putative AII receptors in the SFO also contributing to their particularly severe deficits in thirst induced by AII. (37 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)