The following is a description of how to perform gavage dosing for retinoic acid. Gavage is used when oral administration must be used. It is often used for the administration of oil soluble drugs, like retinoic acid.

DMSO and vegetable oil are immiscible, so it's really an emulsion that is being administered. This emulsion separates out with time (in less than 15 minutes), so be sure to vortex shortly before administration for reproducible results. Blunt needles on a 1 ml syringe are used: the needles are either 20 gauge 1.5 inches with a blunt straight tip Monoject from Sherwood Medical, reorder no 8881-202363; or 20 gauge bulb-tipped feeding needles from Fine Science Tools, Item 18061-20. To administer, the mouse must be gripped firmly by the scruff of the neck, pulling up enough loose skin SO THAT THE MOUSE CANNOT MOVE ITS HEAD--start grabbing the fur down around the shoulders. Immobilize the rest of the mouse in the same hand by pinning the tail between little finger and palm. Insert the needle tip and aim at the back of the throat with the tip--to avoid the trachea. When you feel through the needle that you have gone from the rough, hard palate to the smooth soft palate, straighten out the needle to point to the tail end of the mouse and insert down the esophagous. Don't use force, be patient, keep the needle aligned with the axis of the mouse, the mouse will often relax and swallow to help the needle down. The needle will go in until the base is nearly at the tip of the teeth of an average CD-1 mouse. Inject slowly, then pull straight out.

It would be best if you can find someone skilled to demonstrate. In any case, practise on some stock mice with PBS. If the mouse dies, you either went down the trachea or punctured the GI tract. Usually the mouse seems surprised by the withdrawal of the needle and not terribly upset by the rest of the procedure if it goes smoothly. Mice are most cooperative when it is the low point of their activity cycle in the morning; at the peak of their activity before lights out in the late afternoon they can be difficult. In any case, you can let an upset mouse relax for a bit before trying again.

The biggest barrier to success is your own anxiety. An anxious handler makes for an anxious mouse, and it impairs your performance. Take a deep breath and relax.