In the past ten years, different roles for the enzyme acetylcholinesterase (AChE) have been demonstrated in neuronal function and in important neuropathologies (Alzheimer’s and Parkinson’s disease). The adult cerebral cortex of primates has a particular kind of neurons called Acetylcholinesterase rich-neurons (AChERN). These neurons are located in layers 3 and 5 of the neocortex, they are usually magnopyramidal and have a strong histochemical reaction in the perikaryon and in proximal segments of their processes. AChERN tend to disappear during the progression of Alzheimer’s disease. Previous studies have shown that adult rodents have no AChERN; these are only detected in early stages after birth and they disappear about the 3rd post-natal week. In this study, we have detected AChERN in the adult cerebral cortex of adult Octodon degus (a typical South American rodent). AChERN were found in layers 3 of frontal, parietal and occipital cortices. Using digital morphometry we were able to determine that neurons from the parietal region are larger than frontal neurons. We also compared the size and density of AChERN from human frontal cortex with neurons from frontal cortex of Octodon degus, and found that human AChERN are larger and have a higher density. Previous findings have shown senile plaques and neurofiblrillary tangles in the cerebral cortex of Octodon degus, leading to the conclusion that it provides a natural model of Alzheimer’s disease.
