Kidney Week

Abstract: TH-PO197

Impaired Long-Term and Short-Term Control of Sympathetic Nerve Activity in Nonhypertensive Dahl S Salt-Sensitive Rats

Session Information

• Hypertension and CVD: Basic Research Findings
  October 24, 2024 | Location: Exhibit Hall, Convention Center
  Abstract Time: 10:00 AM - 12:00 PM

Category: Hypertension and CVD

• 1601 Hypertension and CVD: Basic

Authors

• Hutter, Eva, Friedrich-Alexander-Universitat Erlangen-Nurnberg, Erlangen, Bayern, Germany

Eva Hutter, MSc

• Ditting, Tilmann, Friedrich-Alexander-Universitat Erlangen-Nurnberg, Erlangen, Bayern, Germany

Tilmann Ditting, MD

• Meißner, Clara, Friedrich-Alexander-Universitat Erlangen-Nurnberg, Erlangen, Bayern, Germany

Clara Meißner

• Cordasic, Nada, Friedrich-Alexander-Universitat Erlangen-Nurnberg, Erlangen, Bayern, Germany

Nada Cordasic

• Linz, Peter, Friedrich-Alexander-Universitat Erlangen-Nurnberg, Erlangen, Bayern, Germany

Peter Linz, PhD

• Hilgers, Karl F., Friedrich-Alexander-Universitat Erlangen-Nurnberg, Erlangen, Bayern, Germany

Karl F. Hilgers, MD, FASN

• Schiffer, Mario, Friedrich-Alexander-Universitat Erlangen-Nurnberg, Erlangen, Bayern, Germany

Mario Schiffer, MD, DrMed, MBA

• Amann, Kerstin U., Friedrich-Alexander-Universitat Erlangen-Nurnberg, Erlangen, Bayern, Germany

Kerstin U. Amann, MD

• Veelken, Roland, Friedrich-Alexander-Universitat Erlangen-Nurnberg, Erlangen, Bayern, Germany

Roland Veelken, MD, DrMed

• Rodionova, Kristina, Friedrich-Alexander-Universitat Erlangen-Nurnberg, Erlangen, Bayern, Germany

Kristina Rodionova, MD

Background

Our recent research on neurons with afferent dendrites from the kidneys as well as direct renal nerve recordings suggested that the afferent renal innervation tonically inhibits sympathetic activity under normal conditions. Now, we wanted to test the hypothesis that the afferent renal innervation is already impaired in prehypertensive salt-sensitive Dahl S rats receiving a normal salt diet.

Methods

Prehypertensive Dahl salt sensitive rats (DSS) and Sprague-Dawley (SD) controls were kept on normal salt diet. Dorsal root ganglion neurons (Th11-L2) with dendrites from the kidney of both groups of rats were investigated in voltage clamp mode to assess inward currents and current clamp mode to assess action potential (AP) generation. Neurons were classified as tonic (high AP generation upon stimulation) or phasic (AP < 5 upon stimulation). Measurement of arterial blood pressure, heart rate, and direct recordings of renal sympathetic nerve activity (RSNA) were performed in both groups of rats (n=6). To assess neural control of volume homeostasis, rats underwent volume expansion (VE) (0.9% NaCl; 5% of body weight in 30 min) to decrease RSNA.

Results

In vitro, the portion of tonic highly active neurons was significantly smaller in DSS than in SD rats suggesting decreased afferent renal nerve activity (24 % tonic neurons in DSS vs. 51% in SD, *p<0.05, z-test). In vivo, the initial decrease of RSNA during volume expansion was similar for both groups, but RSNA in DSS rats returned to control levels within 15 minutes after cessation of VE but remained significantly decreased in SD rats.

Conclusion

In salt sensitive Dahl S rats on a normal salt rat chow, renal sympathetic nerve activity was likely insufficiently controlled by long term (tonic sympathoinhibitory renal afferent nerves) as well as short term (cardiopulmonary reflex) regulatory mechanisms. These findings suggest a severely impaired function of the autonomous nervous system even in the prehypertensive phase of salt sensitve Dahl S rats.