Discharge of RVLM vasomotor neurons is not increased in anesthetized angiotensin II-salt hypertensive rats

Gustavo R. Pedrino, Alfredo S. Calderon, Mary Ann Andrade, Sergio L. Cravo, Glenn M. Toney

Research output: Contribution to journalArticlepeer-review

7 Scopus citations

Abstract

Neurons of the rostral ventrolateral medulla (RVLM) are critical for generating and regulating sympathetic nerve activity (SNA). Systemic administration of ANG II combined with a high-salt diet induces hypertension that is postulated to involve elevated SNA. However, a functional role for RVLM vasomotor neurons in ANG II-salt hypertension has not been established. Here we tested the hypothesis that RVLM vasomotor neurons have exaggerated resting discharge in rats with ANG II-salt hypertension. Rats in the hypertensive (HT) group consumed a high-salt (2% NaCl) diet and received an infusion of ANG II (150 ng·kg-1·min-1 sc) for 14 days. Rats in the normotensive (NT) group consumed a normal salt (0.4% NaCl) diet and were infused with normal saline. Telemetric recordings in conscious rats revealed that mean arterial pressure (MAP) was significantly increased in HT compared with NT rats (P<0.001). Under anesthesia (urethane/chloralose), MAP remained elevated in HT compared with NT rats (P <0.01). Extracellular single unit recordings in HT (n = 28) and NT (n = 22) rats revealed that barosensitive RVLM neurons in both groups (HT, 23 cells; NT, 34 cells) had similar cardiac rhythmicity and resting discharge. However, a greater (P <0.01) increase of MAP was needed to silence discharge of neurons in HT (17 cells, 44 ± 5 mmHg) than in NT (28 cells, 29 ± 3 mmHg) rats. Maximum firing rates during arterial baroreceptor unloading were similar across groups. We conclude that heightened resting discharge of sympathoexcitatory RVLM neurons is not required for maintenance of neurogenic ANG II-salt hypertension.

Original languageEnglish (US)
Pages (from-to)H1781-H1789
JournalAmerican Journal of Physiology - Heart and Circulatory Physiology
Volume305
Issue number12
DOIs
StatePublished - Dec 15 2013

Keywords

  • Angiotensin II
  • High-salt diet
  • Hypertension
  • Rostral ventrolateral medulla vasomotor neurons
  • Single unit recording
  • Sympathetic nerve activity

ASJC Scopus subject areas

  • Physiology
  • Cardiology and Cardiovascular Medicine
  • Physiology (medical)

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