Which site is preferred for intravenous injection in mice and why?

• A. Femoral artery for faster systemic distribution.
• B. Carotid artery is easier to access in tiny mice.
• C. Tail vein—relatively accessible and minimizes tissue damage when done correctly.
• D. Saphenous vein is preferred because it is large.

Answer: (C)

The question is asking which site provides reliable intravenous access in mice with the least harm, enabling systemic distribution of the injected substance. The tail vein is best because it is relatively easy to locate and access, especially in typical lab mice, and can be accessed with minimal tissue damage when you restrain the animal properly, keep injections gentle, and use a fine needle. This route allows the substance to enter the venous circulation directly for quick, whole-body distribution without the more invasive steps required for arterial access. In contrast, arteries such as the carotid or femoral require surgical exposure and carry higher risks, including bleeding and greater stress to the animal, and the saphenous vein is smaller and more variable, making reliable IV access harder. With proper technique—warming the tail to dilate the vein, confirming venous entry, and controlling the injection pace—the tail vein provides a safe, efficient route for intravenous injections in mice.