title: Opioid μ-receptors in the rostral medullary raphe modulate hypoxia-induced hyperpnea in unanesthetized rats.
abstract: OBJECTIVE
  It has been suggested that the medullary raphe (MR) plays a key role in the physiological responses to hypoxia. As opioid μ-receptors have been found in the MR, we studied the putative role of opioid μ-receptors in the rostral MR (rMR) region on ventilation in normal and 7% hypoxic conditions.
  
  
  METHODS
  We measured pulmonary ventilation (VE) and the body temperatures (Tb) of male Wistar rats before and after the selective opioid μ-receptor antagonist CTAP (D-Phe-Cys-Tyr-D-Trp-Arg-Thr-Pen-Thr-NH2, cyclic, 0.1 μg per 0.1 μL) was microinjected into the rMR during normoxia or after 60 min of hypoxia.
  
  
  RESULTS
  The animals treated with intra-rMR CTAP exhibited an attenuation of the ventilatory response to hypoxia (430 ± 86 mL kg(-1) min(-1)) compared with the control group (790 ± 82 mL kg(-1) min(-1) ) (P < 0.05). No differences in the Tb were observed between groups during hypoxia.
  
  
  CONCLUSIONS
  These data suggest that opioids acting on μ-receptors in the rMR exert an excitatory modulation of hyperventilation induced by hypoxia.
authors.affiliation: Department of Physiological Sciences, Federal University of Goias, Goiania, GO, Brazil.
authors.forename: M B
authors.initials: MB
authors.lastname: Dias
authors.forename: T B
authors.initials: TB
authors.lastname: Nucci
authors.forename: L G S
authors.initials: LG
authors.lastname: Branco
authors.forename: L H
authors.initials: LH
authors.lastname: Gargaglioni
mesh_terms: D000818:Animals; D001831:Body Temperature; D003243:Consciousness; D004195:Disease Models, Animal; D006985:Hyperventilation / Q000209:etiology* / Q000378:metabolism / Q000503:physiopathology; D000860:Hypoxia / Q000150:complications* / Q000378:metabolism / Q000503:physiopathology; D008297:Male; D008845:Microinjections; D009292:Narcotic Antagonists / Q000008:administration & dosage; D010446:Peptide Fragments / Q000008:administration & dosage; D012123:Pulmonary Ventilation / Q000187:drug effects; D011903:Raphe Nuclei / Q000187:drug effects / Q000378:metabolism* / Q000503:physiopathology; D051381:Rats; D017208:Rats, Wistar; D017450:Receptors, Opioid, mu / Q000037:antagonists & inhibitors / Q000378:metabolism*; D015656:Respiratory Mechanics / Q000187:drug effects; D013004:Somatostatin / Q000008:administration & dosage; D013997:Time Factors
chemical_list: C529311:CTAP octapeptide; D009292:Narcotic Antagonists; C485765:Oprm1 protein, rat; D010446:Peptide Fragments; D017450:Receptors, Opioid, mu; D013004:Somatostatin