Effect of Renal Hypertension on the Preference Threshold of Rats for Sodium Chloride

¹ From the Department of Physiology, Harvard Medical School, Boston, Massachusetts

To determine preference thresholds of normal and hypertensive rats for NaCl solutions a cafeteria or choice experiment was performed in which two bottles of fluid were available to each rat. One bottle (reference) always contained distilled water while the second bottle (test) contained a NaCl solution. The concentration of test solution was changed every 4th day, at least 14 different concentrations being used. Preference thresholds of normal and hypertensive rats were the same and lay between .008 and .016 m. Normotensive rats preferred NaCl solution to water at all concentrations above threshold while hypertensive rats showed the same preference only at concentrations ranging from .016–.090 m. A relative NaCl aversion appeared in the hypertensive rats when the concentration of test solution offered was .090 m or greater. Hence, the NaCl aversion of hypertensive rats cannot be attributed to a difference in acuity in differentiating between NaCl solutions and water. Furthermore, the aversion depends in part on the concentration of NaCl solution given, the aversion threshold being about five times higher than the preference threshold.

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