title: Opioid mu-receptors in medullary raphe region affect the hypoxic ventilation in anesthetized rats.
abstract: Opioids can attenuate the peripheral chemoreceptor-mediated hypoxic ventilatory response (HVR) by acting on central mu-type opioid receptors. Since the medullary raphe region (MRR) expresses abundant mu-receptors and participates in modulating HVR, we tested the role of mu-receptors within the caudal, medial, and rostral MRR (cMRR, mMRR, and rMRR) in modulating the HVR. We recorded cardiorespiratory activities and their responses to isocapnic hypoxia in anesthetized rats before and after local microinjection of DAMGO into the MRR, and intravenous administration of DAMGO (100 microg/kg) alone or coupled with a previous local injection of CTAP. Microinjecting DAMGO into the cMRR or mMRR but not the rMRR significantly attenuated the HVR. However, systemic DAMGO-induced HVR attenuation was not significantly affected by pretreating the cMRR and mMRR with CTAP. Our data suggest that cMRR and mMRR mu-receptors are capable of depressing the HVR, while their contribution to the attenuated HVR by systemic DAMGO is limited.
authors.affiliation: Pathophysiology Program, Lovelace Respiratory Research Institute, 2425 Ridgecrest Drive SE, Albuquerque, NM 87108, USA.
authors.forename: Zhenxiong
authors.initials: Z
authors.lastname: Zhang
authors.forename: Fadi
authors.initials: F
authors.lastname: Xu
authors.forename: Cancan
authors.initials: C
authors.lastname: Zhang
authors.forename: Xiaomin
authors.initials: X
authors.lastname: Liang
mesh_terms: D000701:Analgesics, Opioid / Q000494:pharmacology; D000704:Analysis of Variance; D000758:Anesthesia / Q000379:methods; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D004333:Drug Administration Routes; D020875:Enkephalin, Ala(2)-MePhe(4)-Gly(5)- / Q000494:pharmacology; D000860:Hypoxia / Q000473:pathology*; D008297:Male; D008845:Microinjections / Q000379:methods; D010446:Peptide Fragments / Q000494:pharmacology; D011903:Raphe Nuclei / Q000187:drug effects / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D017450:Receptors, Opioid, mu / Q000378:metabolism*; D012119:Respiration / Q000187:drug effects; D013004:Somatostatin / Q000494:pharmacology
chemical_list: D000701:Analgesics, Opioid; C529311:CTAP octapeptide; D010446:Peptide Fragments; D017450:Receptors, Opioid, mu; D020875:Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; D013004:Somatostatin