Cardiovascular afferent signals and drinking in response to hypotension in dogs

Arterial hypotension stimulates increases in plasma arginine vasopressin (AVP), plasma renin activity (PRA), and water intake in conscious dogs. We have previously reported that increasing left atrial but not right atrial pressure completely blocks the increase in plasma AVP and PRA induced by hypotension. The goal of the present study was to examine the effect of increasing right or left atrial pressure on water intake induced by arterial hypotension. Dogs were prepared with occluding cuffs on the thoracic inferior vena cava, the pulmonary artery, and the ascending aorta. We reduced mean arterial pressure (MAP) 25% below control by either inferior vena cava constriction (IVCC), pulmonary artery constriction (PAC), or ascending aorta constriction (AAC) and measured water intake over a 2-h period. Cumulative water intake during IVCC ( n = 6) and PAC ( n = 6) was 7.8 ± 2.0 and 6.7 ± 2.6 ml/kg, respectively. There was no difference between either the latency or the volume consumed between the two treatments. In contrast, none of the dogs drank during hypotension induced by AAC ( n = 5). Because the degree of arterial baroreceptor unloading was the same in each treatment by design, we conclude that stimulation of left atrial receptors inhibits drinking in response to arterial hypotension but that stimulation of right atrial receptors has no effect on the response in dogs.