Physiological Assessment in Stroke Research - Animal Models of Acute Neurological Injuries: Injury and Mechanistic Assessments - page 77

technique, the needle probe is inserted into the temporalis muscle,
adjacent to the skull. Measurements, however, are highly sensitive
to animal or probe movement and do not give an accurate record-
ing of intracerebral temperature ( 33 ).
For direct measurement of temperature at the level of the
brain, thermistor probes can be directly inserted into the brain
parenchyma. Most new systems utilize telemetry approaches for
long-term monitoring; especially, if brain temperatures are to be
monitored in the awake and freely moving animal. For brain
temperature monitoring in animals that will remain anesthetized, a
similar approach can be used with a needle thermocouple device.
Both of these approaches require microsurgery skills and detailed
knowledge of brain and skull anatomy. Furthermore, the surgical
procedures are invasive and complex by their nature. They also
introduce the risk of infection and unintentional brain injury.
In some large territory stroke models, introducing a temperature
probe does increase the risk of mortality.
Technique
For a pericranial approach to brain temperature monitoring:

Calibrate the needle thermocouple probe (e.g., MLT1406,

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Harvard Apparatus) at two temperatures at the upper and
lower limits of expected range (e.g., 33°C and 38°C) in a water
bath. Calibrate at the beginning of the day before experiments
start and any time after power has been turned off or batteries
have been changed.
Sterilize the needle probe in 70-90% ethanol and rinse with

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sterile normal saline prior to use.
Appropriately anesthetize the animal.

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Introduce the needle probe into the temporalis muscle

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Secure the probe in place with suture.

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For intracerebral temperature monitoring, two approaches are
presented. You can either use a needle thermocouple probe or a
smaller micro-implantable thermocouple probe (e.g., #521757,
Harvard Apparatus) both of which are inserted into the brain
parenchyma. Depending on the nature of the experimental study,
the probe size must be considered carefully. In studies where infarct
volume or neurologic outcomes are not being measured, the nee-
dle probe may be appropriate. Given the size of the needle probe,
it does induce injury that would otherwise confound infarct vol-
ume and outcome measurements. In situations where infarct vol-
ume or neurologic outcomes are being measured, the
micro-implantable devices would likely be more suitable.
Technique
Calibrate and sterilize the probe as noted above.

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Anesthetize the animal.

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