Quantitative histochemistry of brain acetylcholinesterase and learning rate in the aged rat

Using a newly developed method for quantitative acetylcholinesterase (AChE) histochemistry we find a substantial decrease in AChE content in aged rats compared to young controls in the cholinergic cell body regions (the ventral pallidum and the medial septal nuclei) and, to a smaller extent in the projection areas (the cortex and hippocampus). In the same group of aged rats we find a severe deficit in the acquisition of a water maze task. Quantitative histochemistry is a potent method for detecting localized changes in AChE content in otherwise intact, learning-impaired aged rats.