Standardization of methods to record Vagus nerve activity in mice

Abstract

Background: The vagus nerve plays an important role in the regulation of organ function, including reflex pathways that regulate immunity and inflammation. Recent studies using genetically modified mice have improved our understanding of molecular mechanisms in the neural control of immunity. However, mapping neural signals transmitted in the vagus nerve in mice has been limited by technical challenges. Here, we have standardized an experimental protocol to record compound action potentials transmitted in the vagus nerve. Methods: The vagus nerve was isolated in Balb/c and B6.129S mice, and placed either on a hook or cuff electrode. The electrical signals from the vagus nerve were digitized using either a Neuralynx or Plexon data acquisition system. Changes in the vagus nerve activity in response to anesthesia, feeding and administration of bacterial endotoxin were analyzed. Results: We have developed an electrophysiological recording system to record compound action potentials from the cervical vagus nerve in mice. Cuff electrodes significantly reduce background noise and increase the signal to noise ratio as compared to hook electrodes. Baseline vagus nerve activity varies in response to anesthesia depth and food intake. Analysis of vagus neurograms in different mouse strains (Balb/c and C57BL/6) reveal no significant differences in baseline activity. Importantly, vagus neurogramactivity in wild type and TLR4 receptor knock out mice exhibits receptor dependency of endotoxin mediated signals. Conclusions: These methods for recording vagus neurogram in mice provide a useful tool to further delineate the role of vagus neural pathways in a standardized murine disease model.

Vagus nerve spiking activity associated with locomotion and cortical arousal states in a freely moving rat

“…Recordings of VN signals were performed by wrapping the cervical VN with a cuff‐shaped electrode with the electrode contact sites attached to the inside walls of the cylindrical tube (Figure a). This recording method reduced background noise and increased the signal to noise ratio (Caravaca et al., ; Sahin & Durand, ; Silverman et al., ). The open edge of the cuff‐shaped electrode was connected to an electrical board on an electrode assembly attached to the animal's head (Shikano, Sasaki, et al., ).…”

“…Unveiling spike patterns of the vagus nerve is indispensable to further understand the communication between the brain and visceral organs such as the heart (Hayakawa et al, 2011), digestive organs (Campos et al, 2012;Czaja et al, 2006), and the lung (Han et al, 2018;Weijs et al, 2015). In previous studies, recordings of VN spikes have been performed in anesthetized rodent animals (Caravaca et al, 2017;Harreby et al, 2011;McCallum et al, 2017;Silverman et al, 2018). Here, we developed a new method to record electrical spikes from the cervical VN using a cuff-shaped electrode in a freely moving animal, which was integrated with our existing method to record bioelectrical signals from multiple organs, including the brain, cardiac system, breathing system, and skeletal muscle.…”

“…While early studies performed vagus nerve recordings from anesthetized animals (Caravaca et al., ; Harreby, Sevcencu, & Struijk, ; McCallum et al., ; Silverman et al., ), recordings from freely moving animals have been limited due to technical difficulties. To address this issue, we developed a novel recording method that can monitor vagus nerve (VN) spikes with a cuff‐shaped electrode from a freely moving rat.…”

Transient Receptor Potential Ankyrin 1 Mediates Afferent Signals in the Inflammatory Reflex

“…The core body temperature was monitored with a rectal probe and was maintained around 37°C with a heating pad and heat lamp. The vagus nerve was then exposed and placed on the recording electrode as described previously 22,26 .…”

“…Optopharmacological stimulation of the vagus nerve: Mice were induced with general anesthesia using isoflurane at 2.5% in 100% oxygen at a flow rate of 1 L/min and maintained in supine position at 2.0% isoflurane. The left vagus nerve was surgically exposed as described previously 22,26 .Optovin (2 µl of 15 mM) was directly applied on the nerve 2 minutes prior to light stimulation. Animals were subjected to 405 nm light stimulation (1000 mA, 10 hz, with a 10% duty cycle for 5 minutes with an approximate power of 80-85 µW) using Thor Labs LED driver DC4100, with a 405 nm LED model M405L3 (Newton, New Jersey).…”