The Interaction of Behavioral and Physiological Mechanisms in the Restoration of Body Fluid Balance Following Acute Sodium Deficiency

Abstract

<p> Subcutaneous injection of formalin produced acute sodium deficiency in rats, characterized by marked hypovolemia and hyponatremia, due to an extravascular leakage of plasma and destruction of cells at the injection site. This reduction in intravascular fluid volume elicited both behavioral and physiological mechanisms of fluid restoration: sodium appetite and thirst as well as renal retention of sodium and water. Appetite and retention evolved together but intakes continued well after retention ceased and plasma volume and sodium concentration were restored to normal. These results indicate that appetite alone is not a true indicator or need, and that sodium and water balances (intake - excretion) must be considered in defining the deficient state.</p>