title: Chronic mu-opioid receptor stimulation in humans decreases muscle sympathetic nerve activity.
abstract: BACKGROUND
  Opioid-addicted patients undergoing detoxification provide a unique opportunity to assess the effects of chronic opioid receptor stimulation on the sympathetic nervous system. We tested the hypothesis that chronic oral methadone intake decreases resting efferent sympathetic nerve activity to muscle (MSA). Furthermore, we assessed whether this effect is reversed by mu-opioid receptor blockade during antagonist-supported detoxification under general anesthesia.
  
  
  RESULTS
  Fifteen young patients (30+/-1 years old, mean+/-SEM) with a long history of mono-opioid addiction and under oral methadone substitution therapy (65+/-10 mg/d for 21+/-6 months) were selected. Peroneal MSA (microneurography) and catecholamine plasma concentrations (high-performance liquid chromatography) were assessed in the awake state and compared with those of age-matched healthy control subjects. The effects of mu-opioid receptor blockade by naloxone (12.4 mg IV) were determined during propofol anesthesia. Compared with healthy volunteers, resting MSA (4+/-2 versus 22+/-2 bursts/min, P<0.0001) and antecubital venous norepinephrine plasma concentration (100+/-64 versus 256+/-48 pg/mL, P=0.01) were markedly decreased in addicted patients despite similar arterial blood pressure and heart rate. Opioid receptor blockade markedly increased MSA (5+/-2 to 24+/-3 bursts/min) and norepinephrine (49+/-12 to 305+/-48 pg/mL) and epinephrine (13+/-2 to 482+/-67 pg/mL) arterial plasma concentrations as well as mean arterial pressure (82+/-4 to 108+/-3 mm Hg) and heart rate (70+/-3 to 86+/-4 beats/min).
  
  
  CONCLUSIONS
  Chronic mu-opioid receptor stimulation by methadone decreases resting MSA in humans.
authors.affiliation: Abteilung für Anästhesiologie und Intensivmedizin, Biochemisches Forschungslabor, and Klinik für Psychiatrie und Psychotherapie, Universitätsklinikum Essen, Germany. peter.kienbaum@uni-essen.de
authors.forename: P
authors.initials: P
authors.lastname: Kienbaum
authors.forename: T
authors.initials: T
authors.lastname: Heuter
authors.forename: M C
authors.initials: MC
authors.lastname: Michel
authors.forename: N
authors.initials: N
authors.lastname: Scherbaum
authors.forename: M
authors.initials: M
authors.lastname: Gastpar
authors.forename: J
authors.initials: J
authors.lastname: Peters
mesh_terms: D000328:Adult; D001794:Blood Pressure; D004594:Electrophysiology; D004837:Epinephrine / Q000097:blood; D005260:Female; D006339:Heart Rate; D006801:Humans; D008297:Male; D008691:Methadone / Q000627:therapeutic use*; D009132:Muscles / Q000187:drug effects* / Q000294:innervation / Q000378:metabolism; D009270:Naloxone / Q000494:pharmacology; D009292:Narcotic Antagonists / Q000494:pharmacology; D009294:Narcotics / Q000494:pharmacology*; D009638:Norepinephrine / Q000097:blood; D009293:Opioid-Related Disorders / Q000097:blood / Q000534:rehabilitation* / Q000652:urine; D010543:Peroneal Nerve / Q000502:physiology; D017450:Receptors, Opioid, mu / Q000819:agonists* / Q000037:antagonists & inhibitors / Q000502:physiology; D012146:Rest; D013564:Sympathetic Nervous System / Q000187:drug effects* / Q000378:metabolism; D015854:Up-Regulation
chemical_list: D009292:Narcotic Antagonists; D009294:Narcotics; D017450:Receptors, Opioid, mu; D009270:Naloxone; D008691:Methadone; D009638:Norepinephrine; D004837:Epinephrine