ObjectiveTo examine whether acute environmental stress (air-jet stress) modulates the exaggerated natriuresis to volume expansion in conscious borderline hypertensive rats.DesignIntravenous isotonic saline volume expansion was performed with and without superimposed acute air-jet stress in conscious borderline hypertensive rats which had consumed a 1% NaCl diet (normotensive) or an 8% NaCl diet (hypertensive) for 12 weeks.MethodsConscious rats were instrumented for measurement of arterial pressure, renal sympathetic nerve activity and collection of bladder urine.ResultsArterial pressure was greater in the 8% NaCI borderline hypertensive rats than in the 1% NaCl borderline hypertensive rats. In the absence of acute air-jet stress the 8% NaCl borderline hypertensive rats exhibited exaggerated natriuresis and exaggerated inhibition of renal sympathetic nerve activity compared with the 1% NaCl borderline hypertensive rats. Acute air-jet stress increased both arterial pressure and renal sympathetic nerve activity reversibly, and attenuated natriuresis in the 8% NaCl but not in the 1% NaCl borderline hypertensive rats.ConclusionAcute environmental stress (air-jet stress) attenuates exaggerated natriuresis in hypertensive but not in normotensive borderline hypertensive rats via increased renal sympathetic nerve activity.