disposable needle (Harvard Instruments, Columbus, OH). A 10-cm section of PE 10 polyethylene tube (Clay-Adams, Parsippany, NJ) was run through the needle. Following this procedure the needle was removed. Then, a small flange was created in one end of the polyethylene tube. The tube was gently pulled through the medial internal surface of the cheek. Consequently, the flanged end of the cannula rested over the oral mucosae while the remainder exited from the mouth. During the second phase of the surgery, another needle was inserted at the back of the neck and guided subcutaneously to exit close to the site of the tube. Next, the tube was run through the needle, hence exiting on the top of the neck where it was secured with a fast-action adhesive (SuperGlue, Santa Anita, CA). The procedure took approximately 10 m per animal and was conducted under an air-sealed hood. After surgery, rats were treated with a topical antibiotic (Neosporin) and placed in individual holding cages with free access to food and water. These cages were lined initially with paper towels (i.e., first 24 hrs post-surgery) and then with regular pine shavings. When not subjected to conditioning procedures, animals were housed in these individual
