Structural, functional and behavioral impact of allergic rhinitis on olfactory pathway and prefrontal cortex

Area of Science:

• Neuroscience
• Immunology
• Ophthalmology

Background:

• Allergic rhinitis (AR) is linked to olfactory dysfunction, sleep disturbances, cognitive decline, and mental health issues.
• The olfactory pathway may connect nasal inflammation to central nervous system (CNS) changes.
• Research is needed to understand AR's impact on the olfactory system and related brain areas.

Purpose of the Study:

• To investigate structural, functional, and behavioral alterations in the olfactory pathway and associated brain regions in a rat model of AR.
• To explore the link between nasal inflammation and CNS modifications via the olfactory system.

Main Methods:

• Allergic rhinitis was induced in Wistar rats using ovalbumin sensitization and challenge.
• Olfactory and behavioral tests were performed.
• Synaptic structure was examined in the olfactory bulb (OB), anterior olfactory nuclei (AON), piriform cortex, and prefrontal cortex (PFC) using immunofluorescence for synaptophysin (Syn) and neuronal markers.

Main Results:

• A significant decrease in Syn optical density was observed in the glomerular layer (GL) of the OB and PFC in AR rats.
• Reduced optical density of GAD67 and VGLUT2 was found in the OB, AON, and PFC.
• AR rats exhibited olfactory dysfunction and reduced male aggressiveness, but no changes in cognition or anxiety-like behavior were detected.

Conclusions:

• Olfactory dysfunction and modified synaptic activity, particularly reduced Syn in the OB and PFC, confirm AR's impact.
• Structural changes in glutamatergic and GABAergic activity were identified in key olfactory pathway components and the PFC.
• These findings highlight the olfactory pathway's role in mediating CNS changes associated with allergic rhinitis.