A Method of Nodose Ganglia Injection in Sprague-Dawley Rat

Summary

Afferent vagal signaling transmits important information to central nervous system from receptors located in organs of the abdomen and thorax. The nodose ganglia of vagus nerves contain many types of receptors that modulate vagal activity. This protocol describes a method of local injections of neurochemicals into the nodose ganglia.

Abstract

Afferent signaling via the vagus nerve transmits important general visceral information to the central nervous system from many diverse receptors located in the organs of the abdomen and thorax. The vagus nerve communicates information from stimuli such as heart rate, blood pressure, bronchopulmonary irritation, and gastrointestinal distension to the nucleus of solitary tract of the medulla. The cell bodies of the vagus nerve are located in the nodose and petrosal ganglia, of which the majority are located in the former. The nodose ganglia contain a wealth of receptors for amino acids, monoamines, neuropeptides, and other neurochemicals that can modify afferent vagus nerve activity. Modifying vagal afferents through systemic peripheral drug treatments targeted at the receptors on nodose ganglia has the potential of treating diseases such as sleep apnea, gastroesophageal reflux disease, or chronic cough. The protocol here describes a method of injection neurochemicals directly into the nodose ganglion. Injecting neurochemicals directly into the nodose ganglia allows study of effects solely on cell bodies that modulate afferent nerve activity, and prevents the complication of involving the central nervous system as seen in systemic neurochemical treatment. Using readily available and inexpensive equipment, intranodose ganglia injections are easily done in anesthetized Sprague-Dawley rats.

Introduction

Afferent signaling via the vagus nerve (cranial nerve X) transmits important general visceral information to the central nervous system (CNS) from baro-, chemo-, hepatic osmo-, cardiac, pulmonary, and gastric receptors located in the organs of the abdomen and thorax. The vagus nerve communicates information from stimuli such as heart rate, blood pressure, bronchopulmonary irritation, and gastrointestinal distension to the nucleus of solitary tract (NTS) of the medulla. The cell bodies of the pseudounipolar neurons of the vagus nerve are located in the nodose and petrosal ganglia, of which the majority is found in the former. Nodose ganglion cells contain a wealth of r....

Protocol

All procedures and protocols were approved by the Institutional Animal Care and Use Committee of the University of Illinois at Chicago. Experiments described here are acute non-survival experiments, and there was no use of eye ointment. Maintenance of sterile conditions only occurs when surgical instruments are washed with 70% ethanol in DiH₂O. Sacrifice of rats at the end of the experiment occurred via overdose of IV ketamine/xylazine.

1. Preparation of Instruments and Chemicals

1. Prepare stock solution of 0.05 M of 5-HT HCl in PBS. Then dilute stock with PBS to a final 5-HT concentration of 0.203 mM.
2. Dilute ....

Results

Figure 1 represents sample breathing recording in rats that had infusion of 5-HT to induce apnea before and after intranodose ganglia injections of dronabinol. 5-HT activates 5-HT₃ receptors on the nodose ganglia that contribute to the Bezold-Jarisch reflex of bradycardia, hypotension, and apnea.^11,17-19 Intranodose ganglia injections of dronabinol activate inhibitory CB receptors, or allosterically modulates 5-HT₃ receptors that inhibit the 5-HT-induced excitation of the.......

Discussion

The critical steps for successful injection of neurochemicals into the nodose ganglia are: 1) identifying and cleaning the connective tissue off the nodose ganglia; 2) confirming the integrity of the nodose ganglia before injection; 3) and using a small gauge needle to delicately inject into, but not completely puncturing through, the nodose ganglia.

The vagus nerve innervates many organs in the neck and abdomen, and relays important information such as heart rate, blood pressure, bronchopulmo.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
5-HT HCl	MP Biomedicals	215376591	12.5 µg/kg per 350 µl/kg
Dronabinol (Marinol) 10 mg Capsules (80 µg/µl)	AbbVie	NDC 0051-0023-21	Dilute with sesame oil to 20 µg/µl
Sesame Oil	Sigma-Aldrich	S3547
Intramedic Polyethylene-50	BD	427411	Ordered from VWR (Cat. # 63019-047)
Graefe Forceps	Roboz	RS-5138	Two are needed
Johns Hopkins Bulldog Clamp	Roboz	RS-7441	Three are needed
Piezoelectric Strain Gauge	Ambu	813255-100
Data Acquisition USB Subsystems	DataWave Technologies
Sciworks Experimenter Software
CyberAmp	Axon Instruments
Syringe, 500 µl, Model 1750 TLL	Hamilton Company	81220
Syringe, 10 µl, Model 1801 RN	7659-01
Needle, 28 G, Small Hub RN	7803-02	Point Style 4, Angle 35, Length 0.5 in