Neutrophil responses to injury or inflammation impair peripheral gustatory function

Area of Science:

• Neuroscience
• Sensory Biology
• Immunology

Background:

• The peripheral taste system exhibits significant functional plasticity following nerve injury.
• Chorda tympani (CT) nerve sectioning causes temporary changes in taste receptor cells, specifically affecting sodium taste transduction.
• Macrophages are involved in recovery, but their presence coincides with functional restoration, suggesting another cell type mediates initial deficits.

Purpose of the Study:

• To investigate the role of neutrophils in modulating neural responses in the intact CT after peripheral taste system injury.
• To determine if neutrophils contribute to the transient sodium taste deficits observed post-nerve injury.

Main Methods:

• Analyzed neutrophil dynamics in response to CT nerve sectioning in rats on control and sodium-deficient diets.
• Depleted neutrophils before nerve sectioning and recorded neural responses from the intact CT.
• Investigated the effect of recruiting neutrophils on taste function.

Main Results:

• Nerve injury transiently increased neutrophils bilaterally; a low-sodium diet amplified and prolonged this response, correlating with persistent sodium taste dysfunction.
• Neutrophil depletion prior to nerve sectioning restored normal sodium taste responses in the uninjured nerve.
• Recruiting neutrophils to the tongue induced sodium taste deficits in both CT nerves.

Conclusions:

• Neutrophils play a critical role in the initial inflammatory response and functional alterations of the peripheral taste system after nerve injury.
• These findings suggest neutrophils, rather than macrophages, are key mediators of early taste changes and plasticity.
• A balanced interplay between neutrophil and macrophage responses is crucial for normal neural function recovery post-injury.