Renal function, heart rate, and blood pressure during exercise and avoidance in dogs.

Abstract

The effects of two behavioral tasks, treadmill exercise and shock avoidance, on renal and cardiovascular function were examined in dogs during intravenous infusion of isotonic saline. Urine was collected with a bladder catheter. Control experiments established steady base lines of urine flow (V), sodium excretion (UNaV), glomerular filtration rate (GFR), free water clearance (CH2O), heart rate (HR), and arterial pressure (Pa). Exercise led to increased V, UNaV, GFR, HR, and Pa with no change in CH2O. Avoidance caused decreases in V and UNaV, increases in HR and Pa but no change in either GFR or CH2O. The hematocrit increased significantly during both tasks. Exercise and avoidance led to opposite urinary changes even when HR accelerations were identical. The natriuretic effect of exercise was the consequence of an increased filtered load, while the antinatriuretic effect of shock avoidance was apparently due to an increased rate of tubular reabsorption of filtrate. The results show that exercise and shock avoidance, while eliciting similar cardiovascular changes, lead to opposite adjustments in urine and sodium output.