SELF-ADMINISTRATION IN MICE

Instrumentation and Software for Research
Self-Administration in Mice
Surgical Procedures and Techniques
CONTENTS
Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . i
Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Surgical Procedure and Cannula Maintenance . . . . . . 2
Further Reading . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Overview
The technique of self-administration is an extremely useful model of human
drug-seeking behavior. It is also the gold standard test for assessing the potential
abuse liability of new pharmaceutical compounds in a preclinical setting.
The self-administration model consists of an operant behavior setup in which a drug
is available, usually via intravenous route, as a reinforcer of some behavioral
response. It is used primarily to predict abuse liability, but also in evaluating treatments
for drug addiction. The model is used effectively in laboratories utilizing rats and
non-human primates. However, the maintenance of chronic intravenous selfadministration has been historically more difficult in mice, despite the abundant
interest in and availability of transgenic mice.
Some laboratories have come up with their own “homemade” methods of getting
good self-administration behavior in mice. Recently, we have checked in with Drs.
Andrew Lawrence and Robyn Brown at the Florey Neuroscience Institutes located
on the campus of the University of Melbourne, Parkville, Australia, who were
generous enough to give us some extra details on the surgical approach utilized
in the Lawrence laboratory.
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Self-Administration in Mice: Surgical Procedures and Techniques | i
Materials
• Inhalation Anesthetic (i.e. 1.5-2% Isoflurane)
• Surgical Instruments
• 3.5 cm length of Silastic® Tubing
Note: When performed by
trained and experienced surgeons,
this procedure should take no
longer than 10 to 20 minutes.
• Limonene
• 22 Gauge Needle
• Sutures
• Silicone
• Instant Adhesive
• Dental Acrylic
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Self-Administration in Mice: Surgical Procedures and Techniques | 1
Catheter Construction
STEP 1:Prepare the Needle
• Prepare a 22 gauge needle by bending it in a “U” shape that is at a
right angle to the Luer hub as shown in Figure 1.
• Blunt the end of the needle by filing off the point so as to prevent puncturing the catheter tubing applied in later steps.
STEP 2:Attach Catheter Tubing to the Prepared 22 Gauge Needle
• Treat the distal end of the Silastic® tubing with limonene, this will soften
the tubing, facilitating attachment to the needle.
• Push the softened end of the catheter tubing over the “U” shaped
needle as shown in Figure 2.
• Apply silicone to the joint of the silastic tubing and the needle.
• Also apply a small ‘ball’ of silicone 1cm from the distal end of the tubing.
STEP 3: Create a cap for the final catheter assembly.
• Saw off the tip of a 1mL syringe and plug with epoxy.
Figure 1: Prepped 22 gauge
needle with blunted end.
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Figure 2: 22 gauge needle
with catheter tubing attached.
Self-Administration in Mice: Surgical Procedures and Techniques | 2
Surgical Procedure and Cannula Maintenance
Surgical Procedure
STEP 1:Insert the Jugular Catheter
• Place the mouse under inhalation anesthesia, such as isoflurane (1.5-2%).
• Once the mouse is completely anesthetized, make an incision along
the midline of the skull.
• Turn the animal over and make an incision below the neck halfway
between the midline and the forelimb.
• Using blunt dissection, isolate the jugular vein.
• Feed the catheter through from the incision on the head such that the
catheter tubing runs subcutaneously over the shoulder from the head to
the jugular vein. The needle end of the catheter should be attached to
a 1mL syringe containing lightly heparinised saline with antibiotic.
• Feed two pieces of suture under the vein, one above and one below the
insertion point, and very loosely tie such that cannulation can still take place.
• Using a stereoscope, insert the catheter tubing 1 cm into the jugular
vein and anchor with suture.
• Test that the catheter is appropriately inserted and anchored by gently
pulling the syringe in and out to test that blood moves back and forth.
Figure 3: Assembled catheter
being fed through the head
incision to the jugular.
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Self-Administration in Mice: Surgical Procedures and Techniques | 3
STEP 2: Position the Catheter and Seal the Incision
• Turn the animal over and affix the bottom of the curved needle to the
skull with instant adhesive, followed by dental acrylic (Figure 4). Build
up a solid base of dental acrylic to keep the catheter firmly in place
(Figure 5).
• Plug the needle luer with the specialized cap prepared prior to surgery.
Figure 4: Needle secured
in place and catheter tubing
inserted 1 cm into the jugular
vein.
Figure 5: Final catheter
assembly secured with dental
acrylic.
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Self-Administration in Mice: Surgical Procedures and Techniques | 4
Post-Surgical Recovery and Maintenance
RECOVERY:
• Allow 3-4 days for recovery, flushing the catheter twice daily with heparinised saline in order to maintain catheter patency.
• After recovery, mice can be maintained in self-administration experiments
for 3-4 weeks.
Maintenance:
• To maintain the cannula after surgery and between uses, flush twice
daily (typically before and after self-administration sessions) with heparinised saline.
• Seal the port with the removable plug when not in session.
• Note: Catheter patency is tested using a mix of ketamine/midazolam.
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Self-Administration in Mice: Surgical Procedures and Techniques | 5
Further Reading
Brown RM, Lawrence AJ (2012). Intravenous Self-Administration of Drugs of
Abuse in Mice. MedLines Newsletter Summer 2012
Brown RM, Stagnitti MR, Duncan JR, Lawrence AJ (2012). The mGlu5 receptor
antagonist MTEP attenuates opiate self-administration and cue-induced
opiate-seeking behavior in mice. Drug Alcohol Depend Jun 1;123(1-2):264-8.
Brown RM, Short JL, Cowen MS, Ledent C, Lawrence AJ (2009). A differential role
for the adenosine A2A receptor in opiate reinforcement versus opiate-seeking
behavior. Neuropsychopharmacology 34: 844-856.
Cahir E, Pillidge K, Drago J, Lawrence AJ (2011). The necessity of alpha4*
nicotinic receptors in nicotine-driven behaviors: dissociation between reinforcing
and motor effects of nicotine. Neuropsychopharmacology 36(7): 1505-1517.
Madsen H, Brown RM, Short JL, Lawrence AJ (2012). Investigation of the neuroanatomical substrates of reward-seeking following protracted abstinence in mice.
J. Physiol., May 1;590(Pt 10):2427-42.
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