Intravenous catheter surgery

Chronic intravenous jugular catheter implantation was performed as previously described (40). Briefly, the rats were anesthetized with 1 to 3% isoflurane in an oxygen mixture. Incisions were made to expose the right jugular vein. A catheter that was made from silicon tubing (inner diameter, 0.5 mm; outer diameter, 0.9 mm) was subcutaneously positioned. After insertion into the vein, the proximal end of the catheter was anchored with surgical silk to the muscles under the vein. The distal end of the catheter was attached to a stainless steel cannula that was bent at a 90° angle. The cannula was inserted in a support that was made with dental cement on the back of the rats. For 1 week after surgery, the rats were treated daily with 0.2 ml of the antibiotic cefazolin (262 mg/ml). For the duration of the experiments, the catheters were flushed daily with 0.2 to 0.3 ml of heparinized saline solution. Body weights were monitored every day, and catheter patency was confirmed approximately every 15 days with an injection of 0.2 to 0.3 ml of Brevital sodium solution (10 mg/ml). Catheter patency was assumed if there was an immediate loss of reflexes. The self-administration experiments began 1 week after surgery.