List of Equipment:

• Syringes (for injection and preparation)
• 18-19 G needle (for preparation)
• 27 G needles (for injection)
• Vortex
• Saline (100μL/250,000 cells)
• Infrared (IR) lamp (for warming up mice)
• Empty cage (for transferring mice after injection)
• Mouse restrainer
• Marker
• Follow-up pages (for recording injection volume, weight, and other details)
• Scales
• Pad gauze
• Alcohol (70%) for hand hygiene

Procedure:

1. Weigh the mouse and fill out the necessary paperwork.
2. Warm up the mice for 10 minutes by exposing them to an infrared (IR) lamp from 10 cm. A Pro Tip: This step is critical because proper preparation leads to success! Do not forget to remove the green lid and the housing from the cage)
3. Vortex the tubes with the cell suspension and use an 18-19G needle to collect the fluid. Change to a 27G injection needle. Discard any excess back into the tube so that just 100μL would stay in the syringe. NB. Check for bubbles and remove any excess fluid, as this can help verify the plunger’s ease of use.
4. Align the tip of the 27G needle with the scale on the syringe facing upwards.
5. Place the restrainer on the table border, ensuring that the border of the restrainer is aligned with the table border.
6. Transfer the mouse tail-first to the restrainer. Keep the mouse by tail basis firmly and locate the side veins.
7. Move your fingers down the tail slightly, but maintain tension to uncover the first third of the tail near the basis.
8. Align the needle with the syringe so the tip hole is parallel to the tail, facing upwards (180°).
9. Insert the needle into the vein, ensuring that it goes in at least 75% of the way to make it stable.
10. Gently pull the plunger backward to observe a flashback of blood. If no flashback is observed, try moving the needle back and forth until a flashback is seen.
    Pro Tip: Only inject the content of the syringe after confirming the flashback.
11. After confirming the flashback, dispense the content of the syringe into the vein.
12. Apply pressure with a pad gauze to prevent bleeding while marking the mouse with a marker. Then, place the mouse in an empty follow-up cage.

A Pro Tips:

• Based on my experience, if you’re working with mice, it is essential to have a reliable restrainer to ensure safety, comfort, and successful technique. I highly recommend the BrainTree Tailveiner® Restrainer for Mice (TV-150 STD). In my opinion, it’s the best option out there, and it’s my personal favorite. Make sure to use a good restrainer, as it’s the most crucial piece of equipment you’ll need.

• Before starting, ensure that the mouse is properly warmed up. Check heating lamps before because they differ by their heating strength.
• Again, inject after confirming the flashback with blood in the syringe/needle.