Protective effect of prior administration of magnesium on delayed hyperalgesia induced by fentanyl in rats.
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.
Van Elstraete
Alain C
AC
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
Sitbon
Philippe
P
Mazoit
Jean-Xavier
JX
Conti
Marc
M
Benhamou
Dan
D
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
D000700:Analgesics; D000701:Analgesics, Opioid; D016194:Receptors, N-Methyl-D-Aspartate; D008278:Magnesium Sulfate; D008274:Magnesium; D005283:Fentanyl