Salt-dependent hypertension in the sinoaortic-denervated rat

To determine the extent to which baroreceptor function is a determinant of salt-dependent hypertension, we studied the cardiovascular and renal responses to increasing dietary sodium chloride in sinoaortic-denervated (n = 9) and sham-denervated (n = 9) Sprague-Dawley rats. Rats were instrumented with an arterial catheter for measurement of arterial pressure and were individually housed for daily measurements of water intake, sodium intake, urinary output, and urinary sodium excretion. Arterial pressure was monitored daily over a 30-minute period by computer. After 3 days of control measurements (0.4% sodium chloride diet), dietary sodium chloride was increased to 8.0% for 21 days, followed by a 3-day recovery period (0.4% sodium chloride). Ingestion of an 8.0% sodium chloride diet resulted in a 20- to 25-fold increase in sodium intake and a fivefold increase in water intake in both groups. In sinoaortic-denervated rats, arterial pressure increased approximately 10 mm Hg on days 5-10, 20 mm Hg on days 11-18, and 30 mm Hg on days 19-21 of 8.0% sodium chloride. Arterial pressure returned to control levels within the first 24 hours of the recovery period. Elevated sodium intake had no significant effect on arterial pressure in the sham-denervated group. Finally, there were no significant differences between groups in urine output or urinary sodium excretion at any time during the study. We conclude that a primary impairment in the afferent limb of the arterial baroreceptor reflex results in salt-dependent hypertension in the Sprague-Dawley rat.