Biology Reference
In-Depth Information
over time. For example, isoflurane is a vasodilator and also may
have neurotoxic effects, while other anesthetics such as xenon
may be neuroprotective.
3. Rat dams will eat the pups if disturbed. This occurs most com-
monly in the first days of life, but can still occur at P7. To mini-
mize this, make sure there is no blood on the pups when they
are returned to the dam after surgery. We have found that wip-
ing the incision with a Betadine swab after incision closure
decreases the likelihood that the dam will interfere.
4. Brain injury in this model can be highly variable, and is extremely
temperature dependent. It is critical to monitor environmental
temperatures closely before, during, and after the experiment.
Small decreases in temperature will produce neuroprotection,
and increases in temperature will increase brain injury. One
solution is to use a plastic hypoxia chamber immersed in a tem-
perature-controlled water bath. In advance, determine the opti-
mal water bath temperature for the chosen chamber. We have
also found that separating the pups during the hypoxia expo-
sure will help ensure uniform temperature, and providing a
heating pad turned to “low” after the experiment for several
days will increase the uniformity of brain injury.
5. The depth and duration of hypoxia will determine the severity
of brain injury. 6-12% oxygen exposure for 30 min to 3.5 h has
been reported. Younger animals are more tolerant of hypoxia
and require longer hypoxia exposures to create injury. Mice are
more susceptible to hypoxic brain injury than are rats, and this
is strain dependent (
57
), so caution must be used when begin-
ning this experimental procedure in new strains. Despite this,
working with mice can be advantageous because they have a
more homogeneous background than rats, and transgenic
strains are available.
6. For short-term experiments, animals can be identified using
permanent marker numbers that are renewed daily. For long-
term experiments, permanent identifiers must be used. Ear
punches or paw tattoos work equally well. For long-term
experiments, weaning at 21-28 days and separation of sexes is
required.
References
1. Edwards AD, Brocklehurst P, Gunn AJ,
Halliday H, Juszczak E, Levene M, Strohm B,
Thoresen M, Whitelaw A, Azzopardi D (2010)
Neurological outcomes at 18 months of age
after moderate hypothermia for perinatal
hypoxic ischaemic encephalopathy: synthesis
and meta-analysis of trial data. BMJ 340:c363
2. Volpe JJ (2009) Cerebellum of the premature
infant: rapidly developing, vulnerable, clinically
important. J Child Neurol 24:1085-1104
3. Tyson JE, Parikh NA, Langer J, Green C,
Higgins RD (2008) Intensive care for extreme
prematurity—moving beyond gestational age.
N Engl J Med 358:1672-1681
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