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Targeting 5HT Receptors Might Control Alzheimer's Dementia

Strategies which target specific 5HT receptors might be helpful in treatment of senile dementia of Alzheimer type.

Compromised serotonergic function might contribute significantly to cognitive decline in senile dementia and in ageing, say specialists in Newcastle upon Tyne, England, and Christchurch, New Zealand. They noted that the cholinergic system was profoundly impaired in senile dementia of Alzheimer type and that replacement therapy had only modest clinical benefits.

The serotonergic system was also impaired, and that might contribute both to cognitive and non-cognitive symptoms in senile dementia of Alzheimer type.

The specialists assessed the effects of lowering brain serotonin by using acute tryptophan depletion on cognitive function in 16 patients who probably had senile dementia of Alzheimer type and 17 healthy, elderly controls.

All received two amino acid drinks, one with tryptophan and one without, in a double-blind, placebo-controlled, crossover study.

Detailed neuropsychological tests were performed 4 to 6 hours after the drink. Mood and other behavioural and emotional symptoms were assessed.

The researchers found that acute tryptophan depletion impaired tasks of working memory in both groups.

No effect was specific to either group. Women with senile dementia of Alzheimer type performed better on a task of pattern recognition during acute tryptophan depletion than with placebo. Behavioural symptoms did not change in either group during tryptophan depletion.
Psychological Medicine 2003;33:41-49. "Effects of acute tryptophan depletion on cognitive function in Alzheimer's disease and in the healthy elderly"

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