The effects of sodium, sympathetic innervation, and central adrenergic structures on the development of changes in renal vascular reactivity were studied in unilaterally nephrectomized rats treated with a single implant of deoxycorticosterone acetate (DOCA; 100 mg/kg). Vascular reactivity to norepinephrine (NE) and vasopressin (ADH) was assessed in isolated kidneys perfused with a synthetic medium. Influence of sodium was determined by placing DOCA-treated rats on high, normal, and low sodium intakes. Neural influence was studied by means of local denervation of the renal artery and by intravenous (iv) and intraventricular (ivt) administration of 6-hydroxydopamine (6-OHDA). Marked changes in renal vascular reactivity in DOCA-treated rats were already apparent prior to the rise in blood pressure. Dose-response curves for NE and ADH showed parallel leftward shifts and decreased threshold doses. Normal sodium intake, local denervation, and peripheral sympathectomy had no effect on the development of these vascular changes in DOCA-treated rats. However, sodium deficiency and ivt administration of 6-OHDA totally prevented development of enhanced vascular reactivity. These results imply that increased vascular reactivity is a major factor in the development of DOCA-hypertension.Circ Res 47: 675-683, 1980