Enteric Nervous System

• The enteric nervous system (ENS) is a complex network of neurons and glia, reminiscent of the central nervous system (CNS), innervating the gut and controlling intestinal function.

• The occurrence of enteric pathology in dementia is well recognised.

• Gastro-intestinal dysfunction, particularly constipation (a clinical expression of enteric neurodegeneration), is a prevalent symptom in neurologic and systemic diseases associated with neurodegeneration. This dysfunction is partly related to abnormalities and cell loss in the ENS.

• Additionally, during aging there is evidence of a loss of excitatory (cholinergic) enteric neurons and interstitial cells of Cajal whereas inhibitory neurons appear unaffected.

• A cholinergic hypothesis of neuronal vulnerability in the CNS is thought to contribute to the cognitive decline seen in aging and neurodegenerative disease.

• Beta amyloid (AB) peptides and it's precursors are well described in the peripheral nervous system including the ENS.

• Recently, a transgenic AD mouse model confirmed the presence of AB in the small and large intestine during aging.

• The ENS may provide a valuable entity to study the pathophysiology of neurodegeneration as well as present as a pathological marker during early stages of AD.