title: Protective effect of prior administration of magnesium on delayed hyperalgesia induced by fentanyl in rats.
abstract: OBJECTIVE
  Magnesium exerts a physiological block of the ion channel on the N-methyl-D-aspartate receptor, and may therefore prevent the induction of central sensitization. The purpose of this study was to assess whether systemic magnesium can prevent long-lasting hyperalgesia induced by sc fentanyl administration in uninjured rats.
  
  
  METHODS
  Long-lasting hyperalgesia was induced in male Sprague Dawley rats with sc fentanyl (four injections, 60 microg x kg(-1) per injection at 15-min intervals). Magnesium sulphate (100 mg x kg(-1)) was injected ip 30 min prior to the first sc fentanyl injection. Sensitivity to nociceptive stimuli (paw-pressure test) was assessed for several days after injections.
  
  
  RESULTS
  Subcutaneous fentanyl led to delayed hyperalgesia associated with a decrease in the nociceptive threshold lasting two days (35% decrease for the maximum effect). Intraperitoneal magnesium sulphate partially but significantly (P < 0.05) prevented the delayed decrease in the nociceptive threshold following sc administration of fentanyl.
  
  
  CONCLUSIONS
  This study shows that magnesium may prevent the delayed and prolonged hyperalgesia following fentanyl administration in rats.
authors.affiliation: Department of Anesthesiology and Biochemistry Laboratory, Hôpital de Bicêtre, Assistance Publique-Hôpitaux de Paris, and the Anesthesia Laboratory UPRES-EA3540, Faculté de Médecine du Kremlin-Bicêtre Université Paris-Sud, Le Kremlin-Bicêtre, France. alainvanel@hotmail.com
authors.forename: Alain C
authors.initials: AC
authors.lastname: Van Elstraete
authors.forename: Philippe
authors.initials: P
authors.lastname: Sitbon
authors.forename: Jean-Xavier
authors.initials: JX
authors.lastname: Mazoit
authors.forename: Marc
authors.initials: M
authors.lastname: Conti
authors.forename: Dan
authors.initials: D
authors.lastname: Benhamou
mesh_terms: D000700:Analgesics / Q000008:administration & dosage / Q000494:pharmacology; D000701:Analgesics, Opioid; D000818:Animals; D005283:Fentanyl; D006930:Hyperalgesia / Q000139:chemically induced / Q000378:metabolism / Q000517:prevention & control*; D055104:Infusions, Subcutaneous; D008274:Magnesium / Q000493:pharmacokinetics; D008278:Magnesium Sulfate / Q000008:administration & dosage / Q000494:pharmacology*; D008297:Male; D017288:Pain Threshold / Q000187:drug effects; D051381:Rats; D017207:Rats, Sprague-Dawley; D016194:Receptors, N-Methyl-D-Aspartate / Q000378:metabolism
chemical_list: D000700:Analgesics; D000701:Analgesics, Opioid; D016194:Receptors, N-Methyl-D-Aspartate; D008278:Magnesium Sulfate; D008274:Magnesium; D005283:Fentanyl