8 August 2009

Study into Parkinson’s disease and dementia

Dysfunction in acetylcholine activity in Parkinson’s disease and dementia
Alzheimer's Australia Dementia News: 6 August 2009
Acetylcholine is a neurotransmitter that transports messages from one nerve cell to another. People with Parkinson’s disease, Parkinson’s disease with dementia with Lewy bodies, and dementia with Lewy bodies are known to have insufficient acetylcholine for normal brain function.

Dr Shimada and colleagues from Chiba University and the National Institute of Radiological Sciences, Chiba, Japan, set out to characterise cholinergic deficits in the brains of people with these diseases. A substance is cholinergic if it can produce, alter, or release acetylcholine, or mimic the behaviour of acetylcholine.

Included in Dr Shimada’s study were 18 people with Parkinson’s disease; 10 people with Parkinson’s disease with dementia with Lewy bodies; 11 people with dementia with Lewy bodies; and 26 healthy controls. Nine of the people in the Parkinson’s disease group were in the early stages of the disease; the other nine patients had advanced Parkinson’s disease. Each study participant was given a brain scan to measure the activity of acetylcholinesterase in the brain. Acetylcholinesterase is an enzyme that degrades acetylcholine, thus stopping transmission between nerve cells.

People with Parkinson’s disease had significantly less acetylcholinesterase activity in the cerebral cortex and especially in the occipital cortex than healthy controls did. But acetylcholinesterase activity in the cerebral cortex was even lower in people with Parkinson’s disease with dementia with Lewy bodies and in others with dementia with Lewy bodies.

When the researchers compared the results from the people with early-stage Parkinson’s with those with advanced Parkinson’s disease, they found no significant difference in acetylcholinesterase activity.

There was also no significant difference between people with Parkinson's disease with dementia with Lewy bodies and others with dementia with Lewy bodies, in the amount by which regional acetylcholinesterase activity in the brain was reduced. Dr Shimada and colleagues concluded that cholinergic dysfunction in the brain occurs in the cerebral cortex, especially in the medial occipital cortex, and that this dysfunction begins in the early stages of Parkinson’s disease. Also, it is more widespread and serious in both Parkinson’s disease with dementia with Lewy bodies and in dementia with Lewy bodies.

Reference: Shimada H, Hirano S, Shinotoh H, Aotsuka A, et al. 2009. Mapping of brain acetylcholinesterase alterations in Lewy body disease by PET. Neurology, 73:273-278.

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