Gut vagal sensory signaling regulates hippocampus function through multi-order pathways

Area of Science:

• Neuroscience
• Gastroenterology
• Psychology

Background:

• The vagus nerve facilitates neural communication between the gastrointestinal (GI) tract and the brain.
• GI signals transmitted via the vagus nerve activate the hippocampus (HPC), a region vital for memory.
• The endogenous role of this GI-vagal-HPC communication in memory remains unclear.

Purpose of the Study:

• To investigate the functional relevance of GI-derived vagal sensory signals in HPC-dependent memory.
• To elucidate the neural pathways mediating gut-to-HPC communication.

Main Methods:

• Selective ablation of GI vagal afferents using saporin (SAP) lesions in rats.
• Assessment of HPC-dependent episodic and spatial memory.
• Measurement of HPC neurotrophic and neurogenesis markers.
• Viral tracing (monosynaptic and multisynaptic) to map neural circuitry.

Main Results:

• GI vagal sensory denervation significantly impaired episodic and spatial memory in rats.
• Lesioned rats exhibited reduced hippocampal neurotrophic and neurogenesis markers.
• Neural tracing identified the medial septum as a key relay in the brainstem-septal pathway connecting the GI tract to the dorsal HPC.

Conclusions:

• Endogenous GI-derived vagal sensory signaling is essential for optimal HPC-dependent memory function.
• A multi-order brainstem-septal pathway mediates this gut-brain communication.
• This study reveals a novel role for the gut-brain axis in regulating memory processes.