Visceral afferents and metabolic function.

Area of Science:

• Neuroscience
• Gastroenterology
• Endocrinology

Background:

• Vagal afferents play a crucial role in relaying information from visceral organs to the central nervous system.
• Understanding the neural regulation of glucose homeostasis and feeding behavior is essential for metabolic research.

Purpose of the Study:

• To investigate the effects of glucose, 2-deoxy-D-glucose (2 DG), cholecystokinin (CCK), and serotonin on the activity of vagal hepatic and pancreatic afferents.
• To explore the potential role of these afferents in sensing blood glucose levels and mediating feeding responses.

Main Methods:

• Electrophysiological recordings of vagal afferent nerve activity in response to systemic administration of glucose, 2 DG, CCK, and serotonin in rabbits, guinea pigs, and rats.
• Analysis of changes in firing rates of hepatic and pancreatic vagal afferents.

Main Results:

• Glucose administration decreased the activity of both hepatic and pancreatic vagal afferents.
• 2 DG administration increased the activity of these afferents, suggesting a role in glucose sensing.
• CCK and serotonin exhibited differential effects, decreasing hepatic afferent activity while increasing pancreatic afferent activity.
• CCK or serotonin-induced decrease in hepatic afferent activity may suppress food intake.
• CCK, serotonin, or insulin-induced increase in pancreatic afferent activity suggests a pancreatic nervous system for circulating substances.

Conclusions:

• Vagal afferents possess mechanisms to respond to blood glucose levels, potentially analogous to lateral hypothalamic neurons.
• CCK and serotonin differentially modulate vagal hepatic and pancreatic afferent activity, impacting feeding behavior and signaling within the pancreas.