Methods to Produce Brain Hyperthermia

Hari Shanker Sharma1

1 Institute of Surgical Sciences University Hospital, Uppsala University, Uppsala
Publication Name:  Current Protocols in Toxicology
Unit Number:  Unit 11.14
DOI:  10.1002/0471140856.tx1114s23
Online Posting Date:  March, 2005
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With the increase in global warming, the problems of hyperthermia have recently attracted world‐wide medical attention. Deaths due to heat‐related illnesses that have occurred in many human populations in recent years are now recognized as a great social and medical problem. Interestingly, the detailed mechanisms of hyperthermia and probable therapeutic measures have still not been worked out. Thus, good experimental models to simulate hyperthermia under clinical conditions are needed to expand our knowledge in the field and to develop suitable therapeutic strategies in the future. This unit describes an animal model to induce hyperthermia that is comparable to the clinical situation. The model will be useful for studying the effects of heat‐related illnesses on various organs and systems. Because hyperthermia is associated with brain dysfunction, methods to assess some crucial parameters of brain injury, such as breakdown of the blood‐brain barrier and brain edema formation, are also described.

Keywords: hyperthermia; brain dysfunction; cell injury; blood‐brain barrier; brain edema; rectal temperature; anesthetics; heat stress; heat stroke

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Table of Contents

  • Basic Protocol 1: Producing Hyperthermia in the Unanesthetized Rat
  • Alternate Protocol 1: Hyperthermia Induced by an Infrared Heat Lamp
  • Alternate Protocol 2: Hyperthermia Induced in Heat Chambers using Anesthetized Animals
  • Support Protocol 1: Postmortem Evaluation of Heat Stress: Microhemorrhages in the Stomach
  • Assessing Changes in Brain Function After Heat Exposure
  • Support Protocol 2: Measuring Blood‐Brain Barrier Permeability to Evans Blue
  • Support Protocol 3: Measurement of Brain Water Content
  • Reagents and Solutions
  • Commentary
  • Literature Cited
  • Figures
  • Tables
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Basic Protocol 1: Producing Hyperthermia in the Unanesthetized Rat

  • Rats or mice (age and sex controlled)
  • Paraffin oil or glycerine
  • 70% (v/v) ethanol
  • Thermistor probe (see ) suitable for rats or mice
  • Waterproof marker
  • Plastic cage, medium size
  • Thermometers, digital or ordinary mercury, with ±0.1°C accuracy
  • Biological oxygen demand (BOD) incubator (e.g., BS Pyromatic India, Asco, Raj Scientific Industries) or comparable heat chamber, preheated to desired temperature (e.g., 38°C)

Alternate Protocol 1: Hyperthermia Induced by an Infrared Heat Lamp

  • Anesthetic (see and see )
  • 75‐, 150‐, or 200‐W infrared lamp

Alternate Protocol 2: Hyperthermia Induced in Heat Chambers using Anesthetized Animals

  • Anesthetic (see and see )

Support Protocol 1: Postmortem Evaluation of Heat Stress: Microhemorrhages in the Stomach

  • Rats or mice, control and heat‐exposed
  • Equithesin solution (see recipe)
  • 2% (w/v) Evans blue solution (see recipe)
  • Physiological (0.9% w/v NaCl) saline, room temperature and 4°C
  • 4% (w/v) paraformaldehyde fixative (see recipe), optional
  • 1‐ml glass or plastic syringes, sterile
  • 26‐ to 28‐G needle (o.d., 0.3 to 0.4 mm)
  • Surgical instruments:
    • Scalpel
    • Forceps
    • Fine scissors
  • Magnifying glass or stereomicroscope
  • Cotton wool, sterile
  • Intravenous perfusion setup, including infusion needle
  • 21‐G butterfly cannula (o.d., 0.8 mm)
  • 2‐ or 3‐way connector, optional
  • Additional reagents and equipment for sectioning rat brain, optional

Support Protocol 2: Measuring Blood‐Brain Barrier Permeability to Evans Blue

  • Dissected rat brains after treatment with Evans blue (see protocol 5), from both control and heat‐stressed animals
  • Laboratory oven, 90°C
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Internet Resources
  A resource for thermistor probes, with links to various suppliers.
  Provides purchasing information for a 3‐mm thermistor probe suitable for rats.
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