The olfactory system and Alzheimer's disease

Area of Science:

• Neuroscience
• Pathology
• Toxicology

Background:

• Alzheimer's disease (AD) is a major health concern with unknown causes and limited treatments.
• Current research lacks a reliable animal model for studying AD.
• The olfactory system's role in AD pathogenesis is under investigation.

Purpose of the Study:

• To explore the hypothesis that viruses or toxins enter the central nervous system (CNS) through the olfactory mucosa.
• To investigate the potential role of excitotoxic phenomena in AD-related neurodegeneration.
• To examine the olfactory system's involvement in the early stages of Alzheimer's disease.

Main Methods:

• Review of existing literature on AD, olfactory system function, and neurotoxicology.
• Analysis of proposed mechanisms of viral/toxic entry and transport within the CNS via olfactory pathways.
• Examination of pathological findings in AD brains, focusing on olfactory and related structures.

Main Results:

• Viruses or toxins may enter the CNS via the olfactory mucosa, reaching olfactory forebrain regions.
• Excitotoxicity, potentially involving glutamate and NMDA receptors, is proposed as a key mechanism of neurodegeneration.
• Early olfactory deficits in AD patients suggest primary involvement of central olfactory structures.

Conclusions:

• The olfactory system, particularly the olfactory mucosa, may serve as a portal of entry for pathogens or toxins implicated in AD.
• Neurodegeneration in AD may initiate in olfactory cortical regions and spread to other brain areas like the hippocampus.
• Olfactory deficits observed in early AD support the hypothesis of olfactory system dysfunction as a precursor to broader neurodegeneration.