Contribution to sympathetic vasomotor tone of tonic glutamatergic inputs to neurons in the RVLM

Jouji Horiuchi, Suzanne Killinger, Roger A L Dampney*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

30 Citations (Scopus)


The role of excitatory amino acid (EAA) receptors in the rostral ventrolateral medulla (RVLM) in maintaining resting sympathetic vasomotor tone remains unclear. It has been proposed that EAA receptors in the RVLM mediate excitatory inputs both to presympathetic neurons and to interneurons in the caudal ventrolateral medulla (CVLM), which then provide a counter-balancing inhibition of RVLM presympathetic neurons. In this study, we tested this hypothesis by determining the effect of blockade of EAA receptors in the RVLM on mean arterial pressure (MAP), heart rate (HR), and renal sympathetic nerve activity (RSNA), after inhibition of CVLM neurons. In anesthetized rats, bilateral injections of muscimol in the CVLM increased MAP, HR, and RSNA. Subsequent bilateral injections of kynurenic acid (Kyn, 2.7 nmol) in the RVLM caused a modest reduction of ∼20 mmHg in the MAP but had no effect, when compared with the effect of vehicle injection alone, on HR or RSNA. By ∼50 min after the injections of Kyn or vehicle in the RVLM, the MAP had stabilized at a level close to its original baseline level, but the HR and RSNA stabilized at levels above baseline. The results indicate that removal of tonic EAA drive to RVLM neurons has little effect on the tonic activity of RVLM presympathetic neurons, even when inputs from the CVLM are blocked. Thus the tonic activity of RVLM presympathetic neurons under these conditions is dependent on excitatory synaptic inputs mediated by non-EAA receptors and/or the autoactivity of these neurons.

Original languageEnglish
Pages (from-to)R1335-R1343
Number of pages9
JournalAmerican Journal of Physiology - Regulatory Integrative and Comparative Physiology
Issue number6 56-6
Publication statusPublished - Dec 2004
Externally publishedYes


  • γ-aminobutyric acid
  • Caudal ventrolateral medulla
  • Excitatory amino acid
  • Glutamate
  • Renal sympathetic nerve activity
  • Rostral ventrolateral medulla


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