title: Magnesium sulphate injected subcutaneously suppresses autotomy in peripherally deafferented rats.
abstract: In rats, recent evidence suggests that injury discharge caused by peripheral nerve section releases excitatory amino acids into the spinal cord which in turn influences decisively the development of autotomy, a self-mutilation behaviour directed towards the denervated areas. Autotomy has been proposed as a behavioural correlate of the neuropathic pain which occurs in humans after complete nerve lesions. Mg2+ ions have been shown to offer protection from neurological and degenerative disorders in which excitatory amino acids are putatively involved. To ascertain the preventive value of Mg2+ administration on autotomy, male rats underwent unilateral ligation and transection of the sciatic and saphenous nerves 30 min after being injected subcutaneously (s.c.) with 300 or 600 mg/kg MgSO4 or saline. Thereafter, autotomy was monitored for 8 weeks. Serum, lumbosacral (L1-S1) and brain magnesium levels were analyzed 0, 30, 60, 120, 180, 240, 360 min and 24 h after the s.c. injection of 600 mg/kg MgSO4. Serum magnesium levels increased quickly from 1.02 mM (0 time) to 4.52 mM (at 60 min) and dropped afterwards to reach physiological levels at 6 h. Peak increments in L1-S1 and brain Mg2+ levels were smaller (32% and 30%, respectively) although maintained for at least 6 h. Magnesium pretreatment in a significant and dose-dependent manner (1) largely suppressed autotomy, (2) decreased final autotomy scores, (3) delayed autotomy onset, and (4) decreased the percentage of animals engaged in high autotomy behaviors. The data support a role for excitatory amino acids in determining susceptibility to autotomy and suggest a hopeful way to prevent neuropathic pain in humans after peripheral deafferentation.
authors.affiliation: Departments of Pharmacology, Faculty of Medicine, University of La Laguna, TenerifeSpain Departments of Physiology, Faculty of Medicine, University of La Laguna, TenerifeSpain.
authors.forename: Manuel
authors.initials: M
authors.lastname: Feria
authors.forename: Faustino
authors.initials: F
authors.lastname: Abad
authors.forename: Alberto
authors.initials: A
authors.lastname: Sánchez
authors.forename: Pedro
authors.initials: P
authors.lastname: Abreu
mesh_terms: D000818:Animals; D001921:Brain / Q000378:metabolism; D003714:Denervation; D007279:Injections, Subcutaneous; D008278:Magnesium Sulfate / Q000008:administration & dosage / Q000493:pharmacokinetics / Q000494:pharmacology*; D008297:Male; D009475:Neurons, Afferent / Q000502:physiology*; D010146:Pain / Q000523:psychology*; D010525:Peripheral Nerves / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012584:Sciatic Nerve / Q000502:physiology; D012652:Self Mutilation / Q000523:psychology*; D013116:Spinal Cord / Q000378:metabolism
chemical_list: D008278:Magnesium Sulfate