Ming, what are the common drug administration methods for mice?

 

Today, let's explore the common injection methods, key operational points, and precautions for mice administration, helping you become more proficient in experimental work!

 

Common Drug Administration Methods in Mice

Methods

I.  Intraperitoneal Injection (IP)
 

 

(Image source: The Laboratory Mouse (Handbook of Experimental Animals))

Procedure:
 

1.  Restrain the mouse: Use dorsal restraint to hold the mouse with its head slightly tilted backward, abdomen facing upward. Secure the left hind limb with your little finger.

2.  Disinfect: Clean the injection site with 75% alcohol swab. Typically select an area 0.5 cm lateral to the midline in the lower abdomen (level with the thigh root).

3.  Insert needle: Insert the syringe needle through the skin. After entering the subcutaneous tissue, advance 2-3 mm along the subcutaneous plane. Insert into the abdominal cavity at a 45-degree angle to the skin. Resistance will disappear once the peritoneum is penetrated.

4.  Aspirate and inject: Aspirate the plunger. If no blood or fluid returns, inject the drug.

5.  Withdraw needle: After injection, gently rotate the needle before slowly withdrawing to prevent leakage.

Precautions:

1.  Ensure accurate injection site to avoid organ injury. Tilting the mouse's head slightly backward helps shift abdominal organs upward.

2.  Insert needle at a downward 45-degree angle, not horizontally or upward, to prevent subcutaneous injection and formation of a bleb.

3.  Wipe the mouse's skin with alcohol before injection. Observe for abnormal reactions after injection.

II.  Intragastric Gavage (IG)
 

 

(Image source: The Laboratory Mouse (Handbook of Experimental Animals))

Procedure:
 

1.  Fasting: Fast mice for 4-8 hours before gavage to prevent gastric contents from obstructing the procedure and affecting drug absorption rate.

2.  Restrain mouse: Position the mouse vertically with head, neck, and body aligned. Pull the tail with your right hand. Grasp the dorsal and neck skin with the thumb, index, and middle fingers of your left hand. Use your ring and little fingers to secure the tail.

3.  Insert needle: Hold the gavage needle with your right hand. Insert from the corner of the mouth, gently press the tongue base, and advance slowly along the posterior pharyngeal wall into the esophagus. There should be no resistance. If resistance is felt or the animal struggles, withdraw and reinsert.

4.  Inject drug: Confirm correct needle placement, then inject the drug slowly. Observe for abnormal reactions during injection.

5.  Withdraw needle: Gently remove the gavage needle after completion. Check for leakage and monitor the mouse's health status.
 

Precautions:
 

1.  The gavage needle tip has a hollow metal ball to prevent insertion into the trachea or damage to the digestive tract.

2.  Insert to appropriate depth, typically 3-4 cm for mice.

3.  Avoid rapid injection to prevent vomiting.

III. Subcutaneous Injection (SQ)
 

(Image source: The Laboratory Mouse (Handbook of Experimental Animals))

Procedure:
 

1.  Restrain mouse: Pinch the dorsal neck skin with your left thumb and index finger to create a taut skin fold.

2.  Disinfect: Clean the injection site with 75% alcohol swab.

3.  Insert needle: Hold the syringe with your right hand, bevel up. Insert at a 45-degree angle to the skin into the subcutaneous space. After insertion, gently wiggle the needle; easy movement indicates subcutaneous placement.

4.  Inject drug: Aspirate to check for blood return. If none, inject slowly. A small bleb will form at the injection site.

5.  Withdraw needle: After injection, withdraw the needle and apply gentle pressure with a sterile cotton swab to prevent leakage.
 

Precautions:
 

1.  Subcutaneous absorption is relatively slow, suitable for drugs with minimal tissue irritation.

2.  Injection sites include the dorsal neck, axilla, or inner thigh.

3.  Injection volume should be 0.1-0.3 ml/10g for mice, less than 1 ml/100g for rats.

IV.  Intravenous Injection (IV)
 

 

(Image source: Laboratory Animal Center, Peking University Shenzhen Graduate School)

Procedure:
 

1.  Restrain mouse: Place the mouse in a restrainer with the tail naturally exposed.

2.  Prepare vessel: Immerse the tail in 45-50°C warm water for 30 seconds, or wipe with 75% alcohol swab to dilate the tail veins.

3.  Insert needle: Hold the syringe with your right hand, bevel up. Insert parallel to the tail vein from the distal end (toward the tail tip). After inserting at least 3 mm, gently push the plunger. If no resistance, proceed with injection.

4.  Inject drug: Inject slowly while observing for abnormal reactions.

5.  Withdraw needle: After injection, apply pressure with a dry cotton ball to prevent bleeding.
 

Precautions:
 

1.  There are three tail veins in mice. The lateral veins are easier to stabilize and commonly used for injection.

2.  Avoid inserting too deeply or puncturing through the vessel, which may cause drug extravasation.

3.  Injection volume is typically 0.1-0.2 ml/10g for mice.

V.  Intramuscular Injection (IM)

 

(Image source: The Laboratory Mouse (Handbook of Experimental Animals))
 

Procedure:
 

1.  Restrain mouse: Usually performed under anesthesia, or with two people: one restraining and one injecting.

2.  Select site: Typically choose the inner or outer thigh muscles of the hind limb.

3.  Disinfect: Clean the injection site with 75% alcohol swab.

4.  Insert needle: Secure the hind limb with your left hand. Hold the needle with your right hand and insert perpendicularly. Aspirate to check for fluid return. If none, inject slowly and evenly.
 

Precautions:
 

1.  Aqueous solutions are rapidly absorbed via IM injection. Suitable for oil solutions and certain irritants.

2.  After injection, gently massage the area around the injection site to promote drug absorption.

VI.  Intradermal Injection (ID)
 

(Image source: The Laboratory Mouse (Handbook of Experimental Animals))
 

Procedure:
 

1.  Restrain mouse: Pinch the dorsal skin with your left hand to create a fold.

2.  Disinfect: Clean the injection site with 70% alcohol swab.

3.  Insert needle: Hold the syringe with your right hand, bevel up. Insert at a 30-degree angle between the epidermis and dermis. Advance 3-5 mm almost parallel to the skin in the subcutaneous plane, then slightly insert further and inject.

4.  Observe: After injection, a small wheal should appear on the skin surface, appearing pale and raised, which disappears after some time.
 

Precautions:
 

1.  Typically choose the skin on both sides of the spine.

2.  Injection volume should not exceed 50 μl. Space injection sites at least 1 cm apart to avoid tissue necrosis.

3.  Do not aspirate the syringe.

 

How to Choose the Appropriate Administration Method

1. Based on Experimental Purpose

● Study oral bioavailability: Choose intragastric gavage.

● Study intraperitoneal bioavailability: Choose IP injection.

● Study acute toxicity: Choose IV or IP injection.

2. Consider Drug Properties

● Water-soluble drugs with minimal irritation: Suitable for IP injection.

● Water-insoluble drugs: May choose IM injection.

● Drugs requiring rapid onset: Choose IV injection.

3. Consider Animal Health Status

● Young or weak mice: Avoid IM injection to prevent muscle damage.

● Long-term administration experiments: May choose SQ injection or gavage.

4. Consider Operational Feasibility

● Technically challenging methods (e.g., IV injection) require skill and experience.

● Simple methods (e.g., gavage) are relatively easy to perform.

 

References:

[1] Laboratory Animal Research Center, Tsinghua University

[2] Experimental Teaching Management Center, Southern Medical University

[3] The Laboratory Mouse (Handbook of Experimental Animals)

[4] https://mp.weixin.qq.com/s/1O9Cjcw9DmhLrskxu0P6gQ

[5] https://mp.weixin.qq.com/s/audrVeCWsrszskJ4OQncDw

[6] https://mp.weixin.qq.com/s/jgqBZ_zw8QfQYwOVfU_Ifg

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