Cardiovascular responses to muscle contraction following microdialysis of nitric oxide precursor into ventrolateral medulla

Benjamin J. Freda, Rajdeep S. Gaitonde, Reshma Lillaney, Ahmmed Ally

Research output: Contribution to journalArticle

27 Scopus citations

Abstract

We determined the effects of administering L-arginine, a precursor for the synthesis of nitric oxide, and L-NMMA (N(G)-monomethyl-L-arginine), a nitric oxide synthase blocker, into the rostral (RVLM) and caudal (CVLM) ventrolateral medulla on cardiovascular responses elicited during static contraction of the triceps surae muscle. Two microdialysis probes were inserted bilaterally into the RVLM or CVLM of anesthetized Sprague-Dawley rats using stereotaxic guides. For RVLM experiments, static muscle contraction evoked by stimulation of the tibial nerve increased mean arterial pressure (MAP) and heart rate (HR) by 29 ± 3 mmHg and 44 ± 7 bpm, respectively (n = 8). Microdialysis of L-arginine (1.0 μM) for 30 min attenuated the contraction-evoked increases in MAP and HR. After discontinuing L-arginine, L-NMMA (1.0 μM) was microdialyzed into the RVLM for an additional 30 min followed by a muscle contraction. This contraction augmented the pressor response (37 ± 4 mmHg) and HR (61 ± 11 bpm) with respect to control values. For CVLM experiments, muscle contraction increased MAP and HR by 23 ± 3 mmHg and 25 ± 5 bpm, respectively (n = 9). Microdialysis of L-arginine (1.0 μM) for 30 min potentiated the contraction- evoked increases in MAP and HR. Subsequent administration of L-NMMA (1.0 μM) into the CVLM for an additional 30 min blocked the augmented MAP and HR responses. Developed tensions did not alter during contractions throughout both RVLM and CVLM protocols. These results suggest that nitric oxide, within the RVLM and CVLM, plays an opposing role in modulating cardiovascular responses during static muscle contraction.

Original languageEnglish (US)
Pages (from-to)60-67
Number of pages8
JournalBrain Research
Volume828
Issue number1-2
DOIs
StatePublished - May 15 1999

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Keywords

  • Arterial blood pressure
  • Caudal ventrolateral medulla
  • GABA
  • Glutamate
  • Heart rate
  • Rostral ventrolateral medulla

ASJC Scopus subject areas

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

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