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Activation of opioid μ‐receptors in the medullary raphe region (MRR) attenuates the ventilatory response to hypoxia in anesthetized rats
Author(s) -
Zhang Zhenxiong,
Xu Fadi,
Zhang Cancan,
Liang Xiaomin
Publication year - 2008
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.22.1_supplement.1172.3
Subject(s) - damgo , microinjection , hypoxic ventilatory response , hypoxia (environmental) , agonist , raphe , medicine , anesthesia , chemistry , ventilation (architecture) , pharmacology , receptor , endocrinology , opioid receptor , respiratory system , serotonin , organic chemistry , engineering , oxygen , serotonergic , mechanical engineering
Caudal (cMRR) rather than medial and rostral MRR (mMRR and cMRR) μ‐receptors (μ‐Rs) were important in attenuating hypercapnic ventilation (V E ) in anesthetized rats. Because opioids attenuate the peripheral chemoreceptor‐mediated early V E response to hypoxia partially via acting on peripheral μ‐Rs, and the MRR is also involved in modulating hypoxic V E , we asked whether local μ‐Rs modulate the early V E response to hypoxia. Cardiorespiratory activities and their responses to 10% O 2 of 1 min were recorded in anesthetized and spontaneously breathing rats before and after: (1) intravenous administration of DAMGO, a μ‐R agonist, alone or coupled with a previous local injection of CTAP, a μ‐R antagonist; and (2) local microinjection of DAMGO. Systemic DAMGO markedly lowered V E and its response to hypoxia by 21% and 30%, respecitvely. V E was reduced only after microinjection of DAMGO into the cMRR, while the hypoxic V E was attenuated by 51% and 27% following microinjection made in the cMRR and mMRR, respectively, and unchanged by rMRR microinjection. Moreover, systemic DAMGO‐induced attenuation of the hypoxic V E was improved by 58% after microinjection of CTAP into both the cMRR and mMRR. Arterial blood pressure and its response to hypoxia were diminished by intravenous rather than MRR local injection of DAMGO. We conclude that activation of μ‐Rs in the cMRR and mMRR can attenuate hypoxic V E (Supported by NIH 74183).