Acute XXXX and natriuretic responses following preoptic hypothalamic lesions.

@entity35 @entity1369 @entity1372 @entity101
The tissue surrounding the anteroventral portion of the third ventricle (the AV3V region) is critical for control of @entity1372 balance and cardiovascular regulation. Ablation of this brain area results in an acute natriuresis and an increase in blood pressure. The purposes of these experiments were to determine the mechanism of the natriuretic response and assess whether the natriuresis contributes to the decreased blood volume following AV3V ablation. @entity35 were instrumented with metal lesioning electrodes in the AV3V region and with catheters in the femoral artery and jugular vein. Following electrolytic lesioning or control procedures, blood pressure, heart rate, urine flow rate and urinary @entity1372 excretion were monitored. In separate groups of animals, plasma and blood volume were measured by calculating dilution of 125I-labelled serum albumin and hematocrit. Results from these studies showed that ablation of the AV3V region resulted in a significant elevation in blood pressure (18 +/- 3 mm Hg), increase in @entity1372 excretion (212 +/- 36 mu Eq/hour), and decrease in plasma volume (10.3 +/- 0.4 mL) compared with control-treated animals (2 +/- 4 mm Hg; 89 +/- 34 mu Eq/h, 12.0 +/- 0.5 mL). This natriuretic response was accompanied by an increased plasma @entity1369 concentration. Further, prevention of the @entity101 response abolished the natriuresis. These data suggest that AV3V ablation produces an acute pressure-mediated natriuresis, resulting in decreases in plasma and blood volume.
