DLAR TRAINING SERIES
INVESTIGATING THE GERBIL
Presented by:
The Division of Laboratory Animal Resources
and
The Animal Investigation Committee
TRAINING SESSION OBJECTIVES
At the completion of this
laboratory, participants should be able to:
-
Confidently
and safely handle and restrain gerbils
-
Determine the
sex of gerbils
-
Be
familiar with the appearance of a normal, healthy animal and be able to
recognize common signs of injury, distress, or illness
-
Apply
methods to identify individual animals
-
Know
how to obtain a blood sample
-
Know
how to administer a SQ, IM, IP, and IV injection
-
Know
what appearance to expect from a gerbil under ketamine/xylazine
anesthesia.
-
Humanely
euthanize a gerbil via IP pentobarbital overdose or carbon dioxide
exposure and provide an assurance of death (i.e., creation of an “open
thoracotomy”, removal of a vital organ).
DIVISION OF LABORATORY ANIMAL RESOURCES
Gerbil Handout
Use this outline to guide you through the variety
of hands-on techniques offered to review and refresh skills and interests.
Comments offered after each technique listed are “keep in minds” for each
procedure. If we haven’t listed a particular technique of interest to you,
don’t hesitate to ask for a demonstration- it’s your wet lab!
I.
Restraint Techniques
-
Grasp near the base of tail to gently lift gerbil out
of cage. Grasping too near the tip of the tail could cause degloving,
exposing the caudal vertebrae.
-
To restrain, apply pressure to the dorsal region of the gerbil while
grasping the skin at the nape of the neck. This will allow you to
restrain the gerbil with one hand and inject with the other.
II.
Ear Tagging
A.
Tag close to head, “numbers up” for greater
visibility.
B.
Unless you ear
tag routinely, you may find it easier to work in pairs; one tagger, one
restrainer.
III.
Injection Techniques
A.
IM- small
volumes, split sites if necessary, avoid sciatic nerve path
B.
SQ- larger
volumes
C.
IP- tilt head
towards floor, use caudal quadrant off midline. Watch syringe hub for
aspirate, discard any contaminated solutions.
D. IV- utilize saphenous veins
located in lateral hock area. Prone to hematoma formation.
IV.
Parenteral
Anesthesia
A. The
anesthetic combination of ketamine and xylazine is commonly used in the
gerbil as it provides good depth of anesthesia with muscle relaxation
which extends into the recovery period. Recommended dose of ketamine/xylazine
in the gerbil is 50 mg/kg and 2 mg/kg IP, respectively.
B. To
calculate your dose, use the formula: weight times dose, divided by
concentration equals volume in ml’s. Example: 0.065 kg (weight) X 50 mg/kg
ketamine (dose) = 3.25 mg divided by 100 mg/ml (concentration) = 0.032 ml
ketamine.
C. Remember
to utilize a bland, sterile ophthalmic base ointment in survival
procedures as ketamine temporarily suppresses the blink reflex which can
lead to corneal drying and scarification.
V.
Blood Collection
A. Saphenous
vein- a tortuous vessel which courses over the lateral aspect of the hock
joint is the only visible collection site in gerbils and can be prone to
hematoma formation. The gerbil may be sedated or manually restrained and
the area over the vessel clipped and prepped with alcohol. The restrainer
may facillitate vessel dilation and stability of the leg by grasping the
loose skin just in front of or behind the leg as it meets the body. A
light coating of sterile ophthalmic ointment is used over the vessel to
cause blood to “well” on the skin instead of dispersing; a 22g or 23g
needle is utilized to simply puncture the vessel. Capillary tubes may be
employed to collect blood as it wells at the site of needle entry. Be sure
to apply gentle pressure to the site for approximately 45 seconds after
collection has been completed to assure hemostasis.
B. Cardiac
puncture- approximate 45 degree needle entry at sternum. Immediately begin
and maintain gentle aspiration pressure. Balance and stabilize
needle placement once puncture has been achieved. This is a terminal
procedure which must be accomplished under general anesthesia and followed
by an assurance of death.
VI. Necropsy (ask if
interested)
GERBIL- Meriones unguiculatus
Origin- Mongolia and northern
China
Description
-
Also called “jirds” or
sand rats
-
Adults weigh 60 – 115
grams (males larger than females)
-
Colors- agouti, black,
gray, white, piebald
Uses
-
Stroke research- easy
to produce cerebral ischemia
-
Epilepsy- spontaneous
seizures precipitated by novel environment or startling
-
Auditory studies-
hearing curve similar to man
-
Lipid metabolism and
heart disease- high serum cholesterol levels
Anatomy
-
Sex by
anogenital distance
-
Males
have dark scrotum
-
Ventral
midline sebaceous gland- covered by stiff orange hairs
-
Adrenal
glands large in relation to total body weight
Physiologic Data
-
Reproduction- polyestrus (every 4 – 6 days),
spontaneous ovulators, gestation 24 days, Wean at 3 weeks, sexually
mature at 10 weeks
-
Antibiotic associated clostridial enterotoxemia is well documented in
the gerbil, use extreme caution with gram positive spectrum antibiotics.
Direct toxicity is caused with streptomycin use and is therefore
contraindicated.
-
Foot
stomping is a method of communication signaling annoyance or aggression
-
Mix
adult animals carefully- severe fighting may result
|
