Reduced hedonic behavior and altered cardiovascular function induced by mild sodium depletion in rats.

Interactions among sodium homeostasis, fatigue, mood, and cardiovascular regulation have been described previously. The present study investigates the effects of sodium deficiency on an index of mood (hypohedonia; Experiment 1), cardiovascular function (Experiment 2), and plasma electrolytes (Experiment 3) in rats. Following 48 hr of sodium depletion with a diuretic (furosemide) and a sodium deficient diet, rats displayed hypohedonia evidenced by reduced responding for rewarding electrical brain stimulation into the hypothalamus. Also, sodium depletion produced increased heart rate and reduced heart rate variability. Plasma sodium levels were lower in sodium-depleted rats versus control rats, whereas potassium levels were unchanged. Thus, mild sodium depletion produces hypohedonia and cardiovascular alterations, which has implications for understanding behavioral and cardiovascular consequences of sodium deficiency.