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Method Description

Intraoral Catheterization and Infusions

Under isoflurane anesthesia, rats (n=16) were implanted with intraoral catheters made of PE-90 tubing that entered the mouth through the lateral check and were externalized on the dorsal surface between the scapulae, as described previously (Eckel and Ossenkopp, 1994). Intraoral catheters were flushed daily with water to maintain patency. For intraoral infusions, rats were weighed and placed in a glass aquarium subdivided into 4 individual compartments by Plexiglas sheets. Syringe pumps infused fluid into the mouth at a rate of 1 ml/min over 6 min. The rats were observed during the intraoral infusions; the time at which the rats first allowed the sucrose to passively drip from their mouths was recorded to the nearest second as the latency to drip. After the infusion, rats and any feces were weighed again as a measure of consumption, and rats were returned to their home cages.

To habituate rats to intraoral infusions, four days after surgery the rats were removed from their home cages and given intraoral infusions of deionized distilled water (6 ml over 6 min) on three consecutive days. After the third water infusion, rats were overnight food-deprived. Rats (n=8) received an infusion of 5% sucrose (6 ml/6 min) followed 30 minutes later by an injection of LiCl (0.15M, 12 ml/kg, i.p.). A separate group of rats received an intraoral infusion of 5% sucrose (6 ml/6 min) followed 30 min later by an injection of NaCl (0.15M, 12 ml/kg, i.p.). Food was returned one hour after the injections. On the final test day, rats recieved an intraoral infusion of 5% sucrose (6 ml / 6 min).

Materials

Intraoral catheter:

PE90 .034" ID .050" OD x 6 inches in length

Intramedic Clay Adams #7421, orderd from VWR #63019-08

Anchor washer for mouth:

PTFE Flat washer Ansi #0 .068 ID .188 OD .025 thick

Small Parts B000FMWA4C $5.56/package of 100

Retaining Washer on back:

instead of using a teflon washer as indicated, we make our own that have smaller ID and larger OD

punch out disc of thin plastic using standard office hole punch; melt hole with hot 21 gauge needle

Silastic sleeve:

.058" ID .077" OD slicone tubing, approx. 1 inch in length

Sliastic adhesive:

Corning Silastic Medical Adhesive Silicone Type A 2 ox/57g tube

Purchased from [www.factor2.com Factor II, inc] #A-100 $31.95

(required considerable paperwork, including affidavit that we wouldn't use in humans.)