Potential Mechanisms of Neuroprotection Induced by Low Dose Total-body Gamma-irradiation in C57 Mice Administered with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)

Low dose total-body gamma-irradiation (TBI) was reported to confer neuroprotection against MPTP-induced dopaminergic neurotoxicity. After being pretreated with a single low dose (0.5Gy, 2.0Gy or 3.5Gy) TBI, C57BL/6 mice were administered with MPTP (15mg/kg, four times, 2h apart) intraperitoneally (i.p.). In the group pretreated with 2.0Gy TBI, with lower lymphocytes number, neuroprotection was found by High Performance Liquid Chromatography (HPLC) determination of the striatal dopamine. Contrarily, in the group pretreated with 0.5Gy TBI, with higher lymphocytes number, dopaminergic neuron toxicity was enhanced. So it was probably the decrease of lymphocytes, not the radiation hormesis that rendered the potential neuroprotection. And it was the balance between radiation injury and lymphocytopenia neuroprotection that decided the effect of low dose gamma-irradiation on MPTP-induced dopaminergic neurotoxicity.