Withdrawal-induced antihypertensive effect of vasopressin in Doca-salt hypertension

Arterial pressure and heart rate were recorded in three groups of conscious unrestrained rats before, during and after a three-hour intravenous infusion of arginine vasopressin (AVP; 20 ng/kg/min). Before infusion of AVP, basal arterial pressure was 152 +/- 3.2 mm Hg for the Doca-salt hypertensive group, 117 +/- 3.2 mm Hg for the uninephrectomized control group, and 111 +/- 2.1 mm Hg for the sham-operated control group. The changes in arterial pressure at each of the time points during the three-hour infusion of AVP were not significantly different among the three groups. Cessation of the AVP infusion was associated with a dramatic and prolonged fall of arterial pressure below preinfusion basal levels in the Doca-salt hypertensive group: pressure was 58 +/- 5.0 mm Hg below basal levels within 60 minutes of stopping the infusion and was still 45 +/- 5.6 mm Hg below four hours later. Pressure in this group was 107 +/- 5.7 mm Hg five hours after stopping the infusion. In contrast, the fall in pressure in the two control groups was small. Five hours after stopping the infusion, pressure was 108 +/- 2.3 mm Hg in the uninephrectomized group and 102 +/- 1.7 mm Hg in the sham-operated group. Thus, five hours after stopping the infusion, blood pressures among the three groups were not significantly different. The Doca-salt hypertensive group had been rendered normotensive.(ABSTRACT TRUNCATED AT 250 WORDS)