Method for measuring cervical vagal nerve activity in conscious rats

Area of Science:

• Neuroscience
• Physiology
• Autonomic Nervous System Research

Background:

• Understanding the interplay between the vagal and sympathetic nervous systems is crucial for homeostasis.
• Direct measurement of cervical vagal nerve activity (cVNA) alongside renal sympathetic nerve activity (RSNA) in conscious subjects is challenging.
• Existing methods may not fully capture the dynamic interactions between these two key autonomic pathways.

Purpose of the Study:

• To propose and validate a novel method for simultaneously measuring cVNA and RSNA in conscious rats.
• To selectively block afferent cVNA to isolate efferent cVNA.
• To investigate the influence of peripherally administered cholecystokinin-8 (CCK-8) on autonomic nerve activity.

Main Methods:

• Surgical exposure of the right cervical vagus nerve in conscious rats.
• Placement of a bipolar electrode for cVNA recording.
• Selective blockade of afferent cVNA using levobupivacaine microcatheter administration.
• Measurement of RSNA and cardiovascular parameters (arterial pressure, heart rate).
• Administration of CCK-8 via intravenous and intraperitoneal routes.

Main Results:

• A method was established to directly measure cVNA and RSNA in conscious rats.
• Levobupivacaine administration successfully reduced cVNA by 84%, enabling selective efferent cVNA assessment.
• Intraperitoneal CCK-8 significantly impacted afferent cVNA without altering RSNA, arterial pressure, or heart rate.
• Intravenous CCK-8 also influenced autonomic nerve activity, with specific effects detailed in the study.

Conclusions:

• The developed technique allows for direct quantification of dynamic changes in vagal and sympathetic nerve activity interactions.
• Peripherally administered CCK-8 modulates central nervous system activity primarily through afferent cVNA.
• This method provides a valuable tool for studying autonomic dysfunction in conditions like obesity and diabetes.