Assay of acetylcholinesterase activity and elemental composition in brain compartments by electron probe microanalysis.
Using histochemical techniques the distribution of acetylcholinesterase (AChE) activity in rat brain has been well established. These assays are based on the precipitation of a specific deposit containing copper-ferricyanide. The amount of locally deposited product is proportional to the AChE activity in the examined area of the section. Thus, the amounts of copper or (and) iron as the deposited histochemical labels mark the distribution and magnitude of the enzyme activity. The present protocol describes an approach to obtain by electron probe microanalysis (EPMA) a map of copper deposited in different brain regions via AChE histochemistry. EPMA allows a wide range of chemical elements to be analyzed. Thus, together with the determination of the copper concentration, elemental contents (Na, Cl, K and Ca) are measured as the specific environment for local AChE activity.