Vagus Nerve Recordings Using Carbon Fiber Microelectrode Array (CFMA)
Ahmad Jiman, Elissa Welle, Paras Patel, David Ratze, Elizabeth Bottorff, Julianna Richie, Zhonghua Ouyang, Dongxiao Yan, John Seymour, Cynthia Chestek, Tim Bruns
Abstract
The carbon fiber microelectrode array (CFMA) has demonstrated promising results in recording single-unti neural activity. This protocol is for obtaining CFMA recordings from the cervical vagus nerve of rats in response to the application of potassium chloride (KCl) on the vagus nerve.
Before start
Steps
Potassium Chloride Solution
0.3mL of potassium chloride (KCl) solution is prepared at a concentration of 2 mEq/mL.
Anesthesia
The animal (Sprague-Dawley female rat) is anesthetised with an intraperitoneal injection of ketamine (90 mg/kg) and xylazine (10 mg/kg). Anesthesia is maintained with a ketamine (30 mg/kg) injection approximately every hour.
Surgical Preparation
A midline cervical incision is made to access the left cervical vagus nerve. Under a dissection microscope, the vagus nerve is isolated (5-7 mm) from the carotid artery and surrounding tissue and placed on a custom 3D-printed nerve holder.
CFMA Insertion
The Carbon Fiber Microelectrode Array (CFMA) is connected to a neural interface processor (Grapevine, Ripple) through a front-end headstage (Nano 2, Ripple). The headstage is controlled by a micromanipulator for accurate insertion of CFMA fibers into the vagus nerve. A small camera (MS100, Teslong) is positioned in the surgical opening to visulaize the alignment and insertion of CFMA fibers into the vagus nerve.
Experiment
Once the CFMA fibers are inserted, a recording trial is intitiated. Forty seconds into the recording trial, 0.3 mL of KCl (2 mEq/mL) is applied on the vagus nerve.
Data Analysis
Recorded signals are sorted for spikes using Plexon Offline Sorter and analyzed using MATLAB to calculates peak-to-peak voltage of spikes, conduction velocity and noise floor.
