Preoptic-hypothalamic periventricular lesions reduce natriuresis to volume expansion

Area of Science:

• Physiology
• Neuroendocrinology

Background:

• Isotonic volume expansion typically triggers natriuresis.
• The anteroventral third ventricle (AV3V) region's role in fluid balance is not fully understood.

Purpose of the Study:

• To investigate if ablating the periventricular tissue around the AV3V affects natriuresis during isotonic volume expansion.
• To determine if the AV3V region is crucial for natriuretic hormone activity and extracellular fluid volume control.

Main Methods:

• Rats underwent electrolytic ablation of the AV3V region or served as controls.
• Intravenous infusion of 0.9% NaCl was administered to induce volume expansion.
• Arterial blood pressure, urine output, and sodium excretion were monitored.
• Plasma extracts were analyzed for natriuretic hormonelike activity using a toad bladder bioassay.

Main Results:

• AV3V-lesioned rats exhibited significantly reduced urinary sodium excretion and urine volume compared to controls during volume expansion.
• Plasma from control animals showed high natriuretic hormonelike activity post-expansion.
• Plasma from AV3V-lesioned rats lacked detectable natriuretic hormonelike activity.

Conclusions:

• Ablation of the AV3V periventricular tissue attenuates the natriuretic response to isotonic volume expansion.
• The AV3V region appears to be a central site critical for natriuretic hormone activity and regulation of extracellular fluid volume.