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Mechanisms of the ventrolateral medulla on the control of sympathetic activity by central chemoreflex in rats
Author(s) -
Moreira Thiago S,
Takakura Ana C,
Menani Jose V,
Sato Monica A,
Colombari Eduardo
Publication year - 2009
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.23.1_supplement.1009.3
Subject(s) - rostral ventrolateral medulla , muscimol , dnqx , chemistry , endocrinology , metabotropic glutamate receptor , medicine , nmda receptor , phrenic nerve , splanchnic , agonist , antagonist , medulla oblongata , anesthesia , receptor , ampa receptor , central nervous system , hemodynamics , respiratory system
In the absence of inputs from carotid bodies and cardiopulmonary receptors hypercapnia markedly increases sympathetic nerve discharge (SND) to the heart and blood vessels. In the present study, splanchnic sympathetic nerve discharge (sSND) and phrenic nerve discharge (PND) were recorded in urethane anaesthetized sino‐aortic denervated and vagotomized rats. Hypercapnia (end‐expiratory CO 2 from 5% to 10%) increased sSND (δ= 103 ± 7%). Bilateral injection of muscimol (GABA‐A agonist ‐ 2 mM in 30 nl) into the retrotrapezoid nucleus (RTN) eliminated PND and reduced the effect of CO 2 on sSND (δ= 56 ± 8%). Injection of AP‐5 (NMDA glutamate receptor antagonist ‐ 100 mM in 50 nl) or DNQX (non NMDA glutamate receptor antagonist ‐ 100 mM in 50 nl) bilaterally into rostroventrolateral medulla (RVLM) reduced PND, but did not change the effect of CO 2 on sSND. Bilateral injection of MCPG (metabotropic glutamate receptor antagonist ‐ 100 mM in 50 nL) into the RVLM reduced PND and the effect of CO 2 on sSND (δ= 41 ± 7%). In conclusion, RVLM metabotropic receptors and RTN are involved in the increase in sSND produced by CO 2 .