Dark Neurons: A protective mechanism or a mode of death

Abstract

More than a century neurons with hyperstaining and compacted feature, dark neurons, have remained as a controversy inclinical and experimental neuropathology studies. Strictly speaking dark neuron formation is characterized with a series ofmorphological features and time-course stainability, but what made them quite bizarre is their non- enzymatic fashion offormation and reversibility. These enigmatic features led to emerging a new theory based on metastability of a gel- likestructure filling the (neuro) cytoplasm. Although based on the gel- gel theory some mysterious aspects of dark neurons couldbe explained, role of receptors and cytoskeleton were not included. In practice, the term dark neuron is often known as the deador degenerating neuron while in contrast more than 90-99 percent of dark neurons recover after a short period of time. Theaim of this review is to give a clear explanation on the morphological features of dark neuron and also provide a theoreticalframework in order to bridge between receptor- cytoskeleton and dark neuron behavior.