Innervation in human taste buds and its decrease in Alzheimer's disease patients

Area of Science:

• Neuroscience
• Histology
• Pathology

Background:

• Taste disorders are common in Alzheimer's disease (AD).
• The specific changes in taste bud innervation in AD are not well understood.
• Immunohistochemistry offers a method to study neuronal markers in taste buds.

Purpose of the Study:

• To investigate the innervation of human foliate and circumvallate papillae taste buds.
• To compare taste bud innervation between Alzheimer's disease (AD) patients and controls.
• To identify suitable neuronal markers for studying taste bud innervation.

Main Methods:

• Immunohistochemical analysis using antisera for protein gene product 9.5 (PGP 9.5), neuron-specific enolase (NSE), tyrosine hydroxylase (TH), dopamine-beta hydroxylase (DbetaH), and calcitonin gene-related peptide (CGRP).
• Studied human foliate and circumvallate papillae from AD and control (ADC) patients.
• Quantified intragemmal nerve fibers using PGP 9.5.

Main Results:

• PGP 9.5 was the most effective marker for identifying intragemmal nerve fibers in taste buds.
• NSE immunoreactivity was found in both nerve fibers and taste bud cells.
• TH- and DbetaH-immunoreactive fibers were absent; CGRP-immunoreactive fibers were rare.
• A significant decrease in PGP 9.5-immunoreactive nerve fibers was observed in the taste buds of AD patients compared to controls.

Conclusions:

• PGP 9.5 is a reliable marker for human taste bud innervation.
• Alzheimer's disease is associated with a significant reduction in taste bud nerve fibers.
• Reduced innervation may contribute to the chemosensory deficits observed in Alzheimer's disease.