Online Electrochemical Measurements of Ca2+ and Mg2+ in Rat Brain Based on Divalent Cation Enhancement toward Electrocatalytic NADH Oxidation

摘要

This study describes a novel electrochemical approach toneffective online monitoring of electroinactive Ca2+ andnMg2+ in the rat brain based on the current enhancementnof divalent cations toward electrocatalytic oxidationnof NADH. Cyclic voltammetry for NADH oxidationnat the electrodes modified with the polymerized filmnof toluidine blue O (TBO) reveals that the current ofnsuch an electrocatalytic oxidation process is remarkablynenhanced by divalent cations such as Ca2+ andnMg2+. The current enhancement is thus used to constitutenan electrochemical method for the measurementsnof Ca2+ and Mg2+ in a continuous-flow systemnwith the polyTBO-modified electrode as the detector.nUpon being integrated with in vivo microdialysis, thenelectrochemical method is successfully applied inninvestigating on cerebral Ca2+ and Mg2+ of livingnanimals in two aspects: (1) online simultaneous measurementsnof the basal levels of Ca2+ and Mg2+ in thenbrain of the freely moving rats by using ethyleneglcolbis(n2-aminoethylether) tetraacetic acid (EGTA) as thenselective masking agent for Ca2+ to differentiate the netncurrent responses selectively for Ca2+ and Mg2+; andn(2) online continuous monitoring of the cerebral Mg2+nfollowing the global ischemia by using Ca2+-maskingnagent (i.e., EGTA) to completely eliminate the interferencenfrom Ca2+. Compared with the existing methodsnfor the measurements of cerebral Ca2+ and Mg2+, thenmethod demonstrated here is advantageous in termsnof its simplicity both in instrumentation and in thenexperimental procedures and near real-time nature,nand is thus highly anticipated to find wide applicationsnin understanding of chemical events involved in somenphysiological and pathological processes.