Sympathoexcitatory CVLM neurons mediate responses to caudal pressor area stimulation

Madhusudan Natarajan, Shaun F. Morrison

Research output: Contribution to journalArticle

47 Scopus citations

Abstract

Neurons in the caudal pressor area (CPA) are a source of tonic sympathoexcitation that is dependent on activation of cardiovascular sympathetic premotor neurons in the rostral ventrolateral medulla (RVLM). In the present study, we sought to clarify the mechanism through which CPA neurons elicit increases in RVLM neuronal discharge, vasoconstrictor sympathetic tone, and arterial pressure. In urethan-chloralose-anesthetized, paralyzed, and artificially ventilated rats, bilateral disinhibition of CPA with bicuculline (Bic) after bilateral disinhibition of caudal ventrolateral medulla (CVLM) caused increases in splanchnic sympathetic nerve activity (+277% control) and arterial pressure (+54 mmHg). Inhibition of CVLM neurons with muscimol abolished the pressor response to activation of CPA neurons, suggesting that neurons within CVLM mediate the excitatory responses from CPA. Disinhibition of CVLM and CPA with Bic enhanced the sympathoexcitatory responses to stimulation of CPA with DL-homocysteic acid, which were blocked by micro-injections of kynurenic acid into CVLM. We conclude that the pathway from CPA to RVLM involves an obligatory glutamatergic activation of sympathoexcitatory neurons in the vicinity of CVLM.

Original languageEnglish (US)
Pages (from-to)R364-R374
JournalAmerican Journal of Physiology - Regulatory Integrative and Comparative Physiology
Volume279
Issue number2 48-2
StatePublished - Sep 20 2000

Keywords

  • Arterial pressure
  • Bicuculline
  • Rostral ventrolateral medulla
  • Sympathetic nerve activity
  • Sympathetic premotor neuron

ASJC Scopus subject areas

  • Physiology
  • Physiology (medical)

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