title: 5-HT1A receptor agonist Befiradol reduces fentanyl-induced respiratory depression, analgesia, and sedation in rats.
abstract: BACKGROUND
  There is an unmet clinical need to develop a pharmacological therapy to counter opioid-induced respiratory depression without interfering with analgesia or behavior. Several studies have demonstrated that 5-HT1A receptor agonists alleviate opioid-induced respiratory depression in rodent models. However, there are conflicting reports regarding their effects on analgesia due in part to varied agonist receptor selectivity and presence of anesthesia. Therefore the authors performed a study in rats with befiradol (F13640 and NLX-112), a highly selective 5-HT1A receptor agonist without anesthesia.
  
  
  METHODS
  Respiratory neural discharge was measured using in vitro preparations. Plethysmographic recording, nociception testing, and righting reflex were used to examine respiratory ventilation, analgesia, and sedation, respectively.
  
  
  RESULTS
  Befiradol (0.2 mg/kg, n = 6) reduced fentanyl-induced respiratory depression (53.7 ± 5.7% of control minute ventilation 4 min after befiradol vs. saline 18.7 ± 2.2% of control, n = 9; P < 0.001), duration of analgesia (90.4 ± 11.6 min vs. saline 130.5 ± 7.8 min; P = 0.011), duration of sedation (39.8 ± 4 min vs. saline 58 ± 4.4 min; P = 0.013); and induced baseline hyperventilation, hyperalgesia, and "behavioral syndrome" in nonsedated rats. Further, the befiradol-induced alleviation of opioid-induced respiratory depression involves sites or mechanisms not functioning in vitro brainstem-spinal cord and medullary slice preparations.
  
  
  CONCLUSIONS
  The reversal of opioid-induced respiratory depression and sedation by befiradol in adult rats was robust, whereas involved mechanisms are unclear. However, there were adverse concomitant decreases in fentanyl-induced analgesia and altered baseline ventilation, nociception, and behavior.
authors.affiliation: From the Department of Physiology, Neuroscience, and Mental Health Institute, University of Alberta, Edmonton, Alberta, Canada (J.R., X.D., J.J.G.); and the Alberta Innovates Health Sciences Foundation, Edmonton, Alberta, Canada (J.J.G.).
authors.forename: Jun
authors.initials: J
authors.lastname: Ren
authors.forename: Xiuqing
authors.initials: X
authors.lastname: Ding
authors.forename: John J
authors.initials: JJ
authors.lastname: Greer
mesh_terms: D000375:Aging / Q000502:physiology; D000698:Analgesia; D018686:Anesthetics, Intravenous / Q000494:pharmacology* / Q000633:toxicity; D000818:Animals; D001143:Arousal; D001522:Behavior, Animal / Q000187:drug effects; D001933:Brain Stem / Q000187:drug effects; D016292:Procedural Sedation; D005283:Fentanyl / Q000037:antagonists & inhibitors* / Q000494:pharmacology / Q000633:toxicity; D066298:In Vitro Techniques; D008526:Medulla Oblongata / Q000187:drug effects; D010147:Pain Measurement / Q000187:drug effects; D010880:Piperidines / Q000494:pharmacology*; D011725:Pyridines / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D044282:Receptor, Serotonin, 5-HT1A / Q000187:drug effects*; D012131:Respiratory Insufficiency / Q000139:chemically induced / Q000517:prevention & control*; D058825:Serotonin 5-HT1 Receptor Agonists / Q000494:pharmacology*; D013116:Spinal Cord / Q000187:drug effects
chemical_list: D018686:Anesthetics, Intravenous; D005283:Fentanyl; D010880:Piperidines; D011725:Pyridines; D044282:Receptor, Serotonin, 5-HT1A; D058825:Serotonin 5-HT1 Receptor Agonists; C473959:befiradol