Jugular vein catheter for i.v. agonist exposure in conscious rats

In some cases, 15-week-old male SH and WKY rats that were implanted with a radiotelemetric device for measuring ECG and dEMG were also implanted during the same procedure with a jugular catheter for intravenous agonist administration. A custom made 18-inch sterile polyethylene catheter (PE50) with a small bubble on one end (serves as an anchor to prevent accidental dislodging) was pre-filled with sterile 0.9% saline and used to cannulate the right exterior jugular vein without damaging the vagus nerve. This catheter allowed for i.v. injection of agonist within the chamber used for exposing the rats to nebulized agonist. The free end of the catheter was sealed using a flame. A 1-inch incision was made on the dorsal side of the neck and a pocket was created. The catheter was then run dorsally under the dermal layers and the extra length was coiled and laid flat in the pocket. The incision was closed using wound clips leaving the end of the catheter exteriorized and secured. The rats were given a recovery period of 7–10 days before any experimentation. Lidocaine was then applied to the dorsal incision site and the coiled length of the catheter was gently exteriorized, recoiled outside of the animal and wrapped with tape to prevent the rat from puncturing the line. The rats were then given 1 hour to acclimate before being exposed to nebulized vehicle and AITC as described above. Ten minutes later rats were administered a 300 μL bolus of vehicle (4% ethanol in PBS, i.v.) and a 300 μL bolus of AITC (9μmol, i.v.) with the injections separated by 10 minutes. ECG and dEMG data were recorded and analyzed as described above.