Cholinergic neuron

A cholinergic neuron is a nerve cell which mainly uses the neurotransmitter acetylcholine (ACh) to send its messages. Many neurological systems are cholinergic. Cholinergic neurons provide the primary source of acetylcholine to the cerebral cortex, and promote cortical activation during both wakefulness and rapid eye movement sleep. In recent years, the cholinergic system of neurons has been a main focus of research in aging and neural degradation, specifically as it relates to Alzheimer's Disease. The dysfunction and loss of basal forebrain cholinergic neurons and their cortical projections are among the earliest pathological events in Alzheimer's Disease.

Most research involving cholinergic neurons involves the basal forebrain cholinergic neurons. However, cholinergic neurons only represent about 5% of the total basal forebrain cell population. Most of these neurons originate in different areas of the basal forebrain and have extensive dendritic fields that project into almost all layers of the cortex. Basal forebrain cholinergic neurons are homologous within a particular basal forebrain region but vary across different regions. In the brainstem acetylcholine originates from the Pedunculopontine nucleus and laterodorsal tegmental nucleus collectively known as the mesopontine tegmentum area or pontomesencephalotegmental complex.

Normal aging is described as aging not accompanied by behavioral or cognitive dysfunctions associated with the cholinergic basal forebrain system. In normal aging, there are beadlike swellings within the cholinergic fibers with enlarged or thickening of the axons, often in grape-like clusters. This fiber swelling can be induced in a laboratory setting by damaging the cell body of the cholinergic neuron, which implies there is a slow cell and fiber degeneration of affected neurons and their projecting axons.

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