Injections
Various routes exist for injecting mice.
Chart of injection routes, sites, volumesand needles
It is important that you discuss theappropriate route, volume, site and needle selection with your veterinarian.
All injections must be described in yourapproved Animal Study Proposal.
All injections must be performed usingsterile needles and syringes.
A new needle and syringe should be used foreach cage of mice.
Intramuscular Injections
Illustration of intramuscular injection formouse Intramuscular Injections
Regardless of the method used forintramuscular injections, it must be noted that the sciatic nerve runs alongthe length of the femur.
It is very important to avoid injuring thisnerve.
This is best accomplished by pointing theneedle, caudally rather than cranially, into the caudal thigh muscles.
It is imperative that the mouse be properlyrestrained.
It is best to swab the area with 70%ethanol before placing the needle and to aspirate to look for blood beforeinjecting.
One of the following methods may be used:
Method #1
Restrain the mouse by the scruff method.
Secure the rear foot nearest to you beneathyour little finger and lower thumb.
Swab the area to be injected with 70%ethanol.
Insert the needle, bevel up, into thecaudal thigh at a 45� angle.
Aspirate to ensure that you have notentered a blood vessel.
If no blood is seen, slowly inject thematerial.
Method #2
Restrain the mouse by the scruff method.
Swab the area to be injected with 70%ethanol.
Insert the needle into the caudal thigh,bevel up.
Aspirate and inject.
Since the foot has not been secured, makesure the mouse does not kick.
Method #3
A technique using two people can also beused for IM injections.
One person restrains the mouse by thescruff method with one hand and steadies the leg to be injected with the other.
The second person identifies the caudalthigh muscles, swabs the area with 70% ethanol, aspirates and injects thematerial.
A tail first restrainer can also be usedfor IM injections.
Gently pull the foot of the leg to beinjected through the restrainer and locate the caudal thigh muscle.
Hold the foot firmly, swab the site with70% ethanol, aspirate and inject the material with the needle bevel up.
SubcutaneousInjections
Restrain the mouse by the scruff method.Use your thumb and forefinger to make a tent of skin over the scruff.
Prep the area with 70% ethanol.
Insert the needle, bevel up, at the base ofthe tent.
The needle should be inserted parallel tothe skin and should be directed toward the posterior of the animal.
Aspirate to ensure proper placement andinject the material.
Revised 4/6/04 9
IntraperitonealInjections
Restrain the mouse by the scruff method.Expose the ventral side of the animal, tilting the head
Prep the site with 70% ethanol.
The sterile needle should be placed, bevelup, in the lower right or left quadrant of the animal abdomen.
Insert the needle at a 30�angle.
Aspirate to ensure proper placement andinject the material.
Intravenous Injections
Warm the mouse under a heat lamp or otherheating device, being sure not to OVERHEAT the animal.
The temperature should not exceed 85 - 90�Fahrenheit at the level of the animal.
Remove the mouse from the heat source immediatelyshould any change in respiration rate or excessive salivation be observed.
Other heating devices, such as disposablehandwarmers, may be used in lieu of a heat lamp.
Place the animal in a restraint device andstabilize the tail between the thumb and forefinger of the hand that will notbe manipulating the syringe.
Prep the tail with 70% ethanol.
Attempt the injection starting at themiddle or slightly distal part of the tail.
With the tail under tension, insert theneedle, bevel up, approximately parallel to the vein and insert the needle atleast 3 mm into the vein.
DO NOT ASPIRATE, as it will cause the vein to collapse.
Inject the material in a slow, fluidmotion.
You should be able to see the vein blanchif the needle is properly positioned.
If any swelling at the injection site orresistance to injection occurs, remove the needle and reinsert
Intradermal Injections
In order to perform intradermal injections,the mouse should be anesthetized.
Shave or pluck an injection site on theback of the animal to remove the hair.
Swab the site with 70% ethanol.
Insert the needle into the skin, bevel up,holding the needle nearly parallel to the plane of the skin.
Do not aspirate.
Inject the material.
The volume of the injection should belimited to 50 ul per site to avoid tissue trauma.
A properly performed intradermal injectionwill result in a small, round skin welt.
Oral Gavage
Gavaging is used to dose an animal with aspecified volume of material directly into its stomach.
Only a specialized, commercially availablegavage needle should be used for attempting this procedure.
Fill the syringe with the appropriatevolume of material and attach the needle.
Restrain the animal by the scruff.
Place the tip or ball of the needle intothe animal mouth.
Slide the tip gently past the back of thetongue.
The needle should slide easily down theesophagus, if properly placed. DO NOT FORCE!!!
If any resistance is met, remove the needleand reinsert.
Do not aspirate.
Once the needle is properly placed,administer the material.
A table of injection routes, sites, volumesand needle sizes can be reached through the link below.
Revised 4/6/04 10
Remember
Select the appropriate restraintmethod, injection route, volume, site and needle gauge for your researchpurposes.
Prep the site with 70%ethanol.
Always inject with theneedle bevel up.
When warming animals, DONOT OVERHEAT.
All injection proceduresmust be described in your Animal Study Proposal.
Consult yourveterinarian for further information concerning injections.
Source: US National Institutes of Health
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