Effect of self-determined intravenous infusion of hypertonic NaCl on Na appetite of sheep.

Abstract

The time delay between a rapid, systemically produced change in Na balance and a change of voluntary Na intake was examined in Na-deficient sheep with a parotid fistula. They were trained to bar press in order to replace a daily Na deficit of 300-500 mmol. During basal conditions on different days, each delivery to a drinking cup consisted of either a small or a large amount of NaCHO3 solution. In the experimental situation, the small amount of NaHCO3 was delivered to the cup, but total Na delivered was made to equal that of the large amount by automatic concurrent i.v. infusion of hypertonic NaCl with each delivery to the cup. As a control, the concurrent i.v. infusion was 0.15 M NaCl, which had little influence on Na balance. A significant difference in the cumulative number of deliveries between the hypertonic and isotonic NaCl infusion conditions occurred by 10-20 min. Systemic injections of hypertonic NaCl are apparently effective within 10-20 min in reducing the Na appetite of Na-depleted animals.