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Opioid receptors modulate excitatory cardiovascular reflex responses to myocardial ATP stimulation through a P2 receptor mechanism
Author(s) -
Fu Liang-Wu,
Barvarz Sherwin,
Ho Jesse,
Longhurst John
Publication year - 2012
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.26.1_supplement.1091.4
Subject(s) - reflex , agonist , medicine , receptor , excitatory postsynaptic potential , endocrinology , opioid , stimulation , p2 receptor , opioid receptor , (+) naloxone , chemistry , anesthesia , pharmacology
Activation of cardiac spinal afferents evokes excitatory cardiovascular reflexes. We have demonstrated that extracellular ATP stimulates ischemia‐sensitive cardiac afferents through P2 receptor mechanisms. The present study tested the hypothesis that through activation of P2 receptors ATP provokes excitatory cardiovascular reflexes and the reflexes are facilitated by blockade of opioid receptors. Hemodynamic parameters were recorded in anesthetized rats after bilateral vagotomy. Intrapericardial injection of α,β‐meATP (31–500 nmol), a P2X receptor agonist, increased mean arterial pressure (MAP) by 4±2 to 49±4 mmHg in a dose‐dependent manner in seven rats. After blockade of cardiac neural transmission with intrapericardial procaine, the α,β‐meATPevoked pressor responses were almost eliminated (n=6). Application of α,β‐meATP‐evoked consistent reflexes in six control rats. Intrapericardial ADP, a P2Y receptor agonist, also increased MAP in five rats by 9 to 13±3 mmHg, although we observed no changes in two and a decrease in two rats. Finally, blockade of opioid receptors with naloxone enhanced the α,β‐meATP‐mediated reflexes from increase in MAP by 27±3 to 37±3 mmHg (n=6). These data suggest that extracellular ATP provokes cardiac sympathetic afferent reflexes mainly through P2X receptor mechanisms and that the magnitude of these reflexes is partially dependent on intact opioid receptors.