Intramuscular injection (IM, IMI) is the administration of the substance using a needle into the muscle layer lying beneath the subcutaneous layer of the skin. Generally speaking, it is unnecessary to anesthesia the mouse for IM. In this protocol, we take the IM in leg as an example to present the experimental procedure of the IM in the mouse as follows. STEP 1
Restrain the mouse, assistance for restraint may be helpful. Secure the rear foot nearest to you beneath your little finger and lower thumb, ensure that one hind leg of the mouse is free and stable for injection. If not, the needle may cause muscle injury or damage when dosing.
STEP 2
The needle should be inserted perpendicular to the skin. Use an appropriate size syringe or needle to inject at a 30° angle and inject the substance into the quadriceps femoris or muscle mass in the outer thigh of the mouse. Please note do not inject into the posterior muscle because it may damage the sciatic nerve.
Drug dosage: No more than 0.1 mL/10g for mice and 0.5 mL/10g for rats.
STEP 3
Aspirate to ensure that you have not entered a blood vessel. If blood is aspirated, redirect the needle and aspirate again. If no blood is aspirated, slowly and stably inject the material.
STEP 4
Withdraw needle and press the injection site with your finger or cotton swab for a while to prevent bleeding.
STEP 5
Return the mouse to its cage. Be careful not to frighten animals during the whole procedure.

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