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The influence of magnesium on morphine-induced stimulation of the reward system Volume 23, numéro 1, March 2010

Auteurs
Department of Pharmacology, University of Medicine and Pharmacy “Gr. T. Popa” Iasi, Romania

The present study was designed to assess the influence of magnesium (Mg) as MgCl 2 (10 or 40 mg/kg b.wt/day i.p.) and of its interaction with morphine on the reward system (RS) in Wistar rats. For this purpose, we evaluated conditioning place preference on a 12 day experiment schedule. Our data show that MgCl 2 (10 mg/kg b.wt/day) has moderate but significant effects on stimulating RS (increasing the time spent in associated conditioned compartment) (327.75 ± 11 s in the Mg (10 mg/kg b.wt) group vs 295.2 ± 8 s in the control (saline) group, p < 0.05) but not at higher Mg doses (40 mg/kg b.wt/day). We tested the influence of MgCl 2 (10 mg/kg b.wt./day i.p.) upon naloxone (2 mg/kg b.wt/ i.p.)-induced place aversion. Administrated alone, naloxone has an aversive effect on place preference. MgCl 2 (10 mg/kg b.wt/day i.p.) has a significantly decreased aversive effect of naloxone (280.7 ± 37 s in naloxone + MgCl 2 (10 mg/kg b.wt) group vs 189 ± 21 s in naloxone group, p < 0.05). MgCl 2 at both tested doses, added to morphine (3 mg/kg b.wt/day i.p), decreased the acquisition of morphine-induced place preference (262.2 ± 17 s) in morphine + MgCl 2 (40 mg/kg b.wt) group vs 462.15 ± 28 s in morphine group, p < 0.05). MgCl 2, 10 mg/kg b.wt/day i.p. decreased both morphine-induced place preference and naloxone-induced place aversion.