Microphotometric dynamic analysis of the histochemical acetylcholinesterase reaction

Dynamic analysis of the histochemical reaction of Karnovsky-Roots for acetylcholinesterase activity (AChE) is reported. Two methods were used. The first method was videography and densitometric analysis of frames from the film. The second method was direct microphotometric analysis of the reaction dynamics by the plug-method (measurement of average light transmission through a limited area of preparation or image). Special microchambers were used on the stage of an inverted microscope. The results showed the dynamics of final product accumulation in two structures of rat caudate nucleus: AChE-positive neuropil and the AChE-negative myelin bundle during histochemical incubation. Videography and densitometry of the digital images allowed morphologic and microphotometric analysis of changes in tissue sections during incubation, and the dynamic analysis permitted the study of enzyme kinetics in situ. Problems associated with microphotometric analysis of digital images for quantitative histochemical studies of the enzyme activity are discussed.