Sympathoinhibition evoked from caudal midline medulla is mediated by GABA receptors in rostral VLM

Matthew J. Coleman, Roger A L Dampney*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

29 Citations (Scopus)

Abstract

The present study was performed to determine whether the powerful depressor and sympathoinhibitory response that can be evoked from neurons in the caudal midline medulla is mediated by γ-aminobutyric acidergic (GABAergic) inhibition of sympathoexcitatory neurons in the rostral part of the ventrolateral medulla (VLM). In anesthetized barointact and barodenervated rabbits, bilateral microinjections of bicuculline into sympathoexcitatory sites in the rostral VLM resulted in a sustained increase in renal sympathetic nerve activity and abolished or reversed the depressor and sympathoinhibitory response evoked by glutamate microinjection into the caudal midline medulla. By contrast, the sympathoinhibitory response evoked from the caudal midline medulla persisted when the background level of renal sympathetic nerve activity was reflexly raised by baroreceptor unloading. The results indicate that 1) the depressor and sympathoinhibitory response evoked by stimulation of neurons in the caudal midline medulla is mediated by a GABAergic synapse in the rostral VLM and 2) there are also sympathoexcitatory neurons in the caudal midline medulla whose presence is revealed by blockade of the more powerful sympathoinhibitory response.

Original languageEnglish
JournalAmerican Journal of Physiology - Regulatory Integrative and Comparative Physiology
Volume274
Issue number2 43-2
Publication statusPublished - Feb 1998
Externally publishedYes

Keywords

  • γ-Aminobutyric acid
  • Baroreceptor reflex
  • Raphe pallidus and obscurus
  • Renal sympathetic nerve activity
  • Ventrolateral medulla

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