The effects of vitamin B₁₂ on the brain damages caused by methamphetamine in mice

Methamphetamine (METH) is a powerful stimulant drug that directly affects the brain and induces neurological deficits. B₁₂ is a water-soluble vitamin (vit) that is reported to attenuate neuronal degeneration. The goal of the present study is to investigate the effect of vitamin B₁₂ on METH's neurodegenerative changes.

Two groups of 6 animals received METH (10 mg/kg, interaperitoneally (IP)) four times with a 2 hr interval. Thirty mins before METH administration, vit B12 (1 mg/kg) or normal saline were injected IP. Animals were sacrificed 3 days after the last administration. Caspase proteins levels were measured by Western blotting. Also, samples were examined by TUNEL assay to detect the presence of DNA fragmentation. Reduced glutathione (GSH) was also determined by the Ellman method.

The pathological findings showed that vit B₁₂ attenuates the gliosis induced by METH. Vit B₁₂ administration also significantly decreased the apoptotic index in the striatum and the cerebral cortex (P<0.001). It also reduced caspase markers compared to the control (P<0.01 and P<0.001, respectively). Interestingly, co-administration of METH and Vit B₁₂ elevates the levels of GSH in both regions of the brain and returned it to normal levels compared to the METH group.

The current study suggests that parenteral vit B₁₂ at safe doses may be a promising treatment for METH-induced brain damage via inhibition of neuron apoptosis and increasing the reduced GSH level. Research focusing on the mechanisms involved in the protective responses of vit B₁₂ can be helpful in providing a novel therapeutic agent against METH-induced neurotoxicity.