Changes in extracellular glutamate and pressor response during muscle contraction following AMPA-receptor blockade in the RVLM and CVLM

Reshma Lillaney, Timothy J. Maher, Pasarapa Chaiyakul, Ahmmed Ally

Research output: Contribution to journalArticle

23 Scopus citations

Abstract

We examined whether modulation of cardiovascular responses by administering 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX, an AMPA-receptor antagonist) into the rostral (RVLM) or caudal (CVLM) ventrolateral medulla are mediated via changes in extracellular levels of glutamate. Microdialysis probes were inserted bilaterally into the RVLM or the CVLM. For the RVLM experiments (n=8), muscle contraction for 2 min increased mean arterial pressure (MAP) and heart rate (HR) by 18±3 mmHg and 24±5 bpm, respectively. Extracellular glutamate concentrations increased from 1.5±0.3 to 4.3±0.9 ng/5 μl during the contraction. Microdialysis of CNQX (1.0 μM) for 30 min into the RVLM attenuated the increases in MAP, HR, and glutamate concentration in response to a muscle contraction (8±2 mmHg, 11±3 bpm, and 2.2±0.7 ng/5 μl, respectively). Developed tensions did not change during contractions before and after CNQX. Microdialysis of CNQX into the CVLM (n=8) potentiated the contraction-evoked responses in MAP (19±3 vs. 34±3 mmHg) and HR (25±4 vs. 49±5 bpm) without a change in developed tension. Following CNQX perfusion into the CVLM, the levels of extracellular glutamate in the CVLM were also augmented during the contraction. Results suggests that AMPA-receptors within the RVLM and CVLM differentially modulate cardiovascular responses during static muscle contraction via increasing and decreasing, respectively, extracellular glutamate concentrations. Copyright (C) 1999 Elsevier Science B.V.

Original languageEnglish (US)
Pages (from-to)164-173
Number of pages10
JournalBrain Research
Volume844
Issue number1-2
DOIs
StatePublished - Oct 9 1999
Externally publishedYes

Keywords

  • Blood pressure
  • Caudal ventrolateral medulla
  • Excitatory amino acid
  • Microdialysis
  • Rostral ventrolateral medulla

ASJC Scopus subject areas

  • Neuroscience(all)
  • Molecular Biology
  • Clinical Neurology
  • Developmental Biology

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