Research progress of Manganese-enhanced MRI optic nerve tracing in vivo

Manganese-enhanced MRI (MEMRI) optic nerve tracing in vivo is a technology which can reflect the axonal transport status and visual pathway connection by utilizing divalent manganese ion’s transportability in axons and its characteristics of paramagnetism, and such potential optic nerve tract-tracing technique has been widely used in ophthalmologic research.Mn²⁺ enters the neurons through the voltage-gating Ca²⁺ channel and is transported by microtubule system which is not depended on cellular electric activity.However, the trans-synaptic transport of Mn²⁺relies on membrane potential.Taking advantages of MEMRI, optic nerve injury-related research could be implemented.Mn²⁺ is an intracellular contrast agent with metal toxicity, so low dose, fractionated, targeted delivery of Mn²⁺ is recommended to alleviate the adverse effects of Mn²⁺ .Herein, the mechanism of divalent manganese ion optic nerve tracing, application of MEMRI in ophthalmologic research field, drug delivery approach of divalent Mn²⁺and its toxicity were summarized.