Effects of Magnesium Oxide Nanoparticles on Depression- Like Behavior Induced by Naloxone and Morphine Withdrawal

Our previous studies indicated that nanoparticles of magnesium oxide (nano-MgO) can affect some of morphine withdrawal signs such as anxiety, but their interaction with opioidergic system activity in depression- like behavior induced by morphine withdrawal is not clear.
The present study aimed at investigating the effects of nano-MgO on depression induced by naloxone and morphine withdrawal in animals.
Adult male NMRI mice were divided in 2 main groups. For the control group, intraperitoneal (i.p.) injection of nano-MgO (1, 2.5 and 5 mg/kg) or naloxone (3 and 5 mg/kg) and coinjections of naolxone5 before and after nano-MgO2.5 mg/kg were done. The morphine withdrawal group received saline or nano-MgO 2.5, 5 and 10 mg/kg as acute (a single injection at the test day) and chronic injection (coinjected with morphine for 4 days). To develop morphine dependency, increasing doses of 20, 40, and 80 mg/kg morphine were injected subcutaneously for 4 days. Then, mice received a final morphine injection (40mg/kg) 3 hours prior to naloxone (5 mg/kg (i.p.)) on the test day. Depression- like behavior was assessed by the tail suspension test.
Naloxone 3 and 5mg/kg induced depression (P