3.3. Delivering siRNA/cationic liposome complex into mice by intravenous injection.

Hold the mice in a standard mouse restrainer.

Stimulate dilation of the tail veins in mice by placing the tail in warm (30–35 ºC) water.

Grasp the tail at the distal end. Place the index and middle fingers of the non-dominant hand around the tail above where the needle will be inserted. Hold the lower part of the tail between the thumb and ring fingers below the injection site.

Slightly oppose pressure with both sets of fingers to straighten and stabilize the tail. Release pressure immediately before injection.

Insert the needle into the vein towards the direction of the head with the dominant hand. Hold the needle and syringe parallel to the tail with bevel side up.

Gently pull blood into the syringe to confirm proper placement in the vessel before injecting. Alternately, verify proper placement by advancing the needle smoothly into the vein without any resistance.

Slowly inject the total siRNA/liposome mixture (see Note 6).

Remove the needle and apply gentle compression until bleeding has stopped.

Return mice to their cage and monitor for an addition 5–10 minutes to ensure that bleeding has not resumed.