Lower Brain Serotonin: A Drive of Cognitive Decline

An estimated 47 million people worldwide have dementia, with the majority of these cases being Alzheimer’s Disease (AD).AD is a neurodegenerative disease characterized by the deterioration of specific nerve cells, the formation of neuritic plaques, and the presence of neurofibrillary tangles. Researchers have previously linked the characteristics of AD to severe declines in serotonergic neurons, but until recently, it was not clear whether these reductions were the cause or effect of the disease.

A study published in Neurobiology of Disease suggests that lower levels of serotonin transporters (SERT) may precede neurodegeneration. Led by Clifford Workman at the Johns Hopkins School of Medicine, the research team compared 28 participants with mild cognitive impairment (MCI) to 28 controls throughout a series of memory tests, MRI scans, and PET scans. Lower SERT levels were observed in the cortical, limbic, and peri-limbic regions of MCI patients compared to healthy controls. Results from the study reveal a strong correlation between SERT levels and scores on the memory test in participants with MCI, suggesting that serotonin is heavily implicated in the early stages of cognitive decline.

The conclusions from the study can be used to improve current methods of treatment for AD. Drugs such as cholinesterase inhibitors help to mask the symptoms of AD. However, they do not treat the underlying disease or slow its progression. Methods to increase serotonin functioning in the brain provide a promising avenue to slow or stop the progression of AD along with other forms of dementia. Studies are in progress to elucidate the mechanism of serotonin in the transition from MCI to dementia and to relate serotonin degeneration to other aspects of AD neuropathology.

Written by Sheila Yu

References may be found in the journal. 

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