A simple method to induce focal brain hypothermia in rats

• Published in: Journal of cerebral blood flow and metabolism 2007-01, Vol.27 (1), p.115-122
• Main Authors: Clark, Darren L, Colbourne, Frederick
• Format: Article
• Language: English
• Subjects: Anesthesia; Anesthesia. Intensive care medicine. Transfusions. Cell therapy and gene therapy; Animals; Biological and medical sciences; Blood Pressure - physiology; Body Temperature - physiology; Brain - physiology; Emergency and intensive care: comas and nervous system diseases; Heart Rate - physiology; Hypothermia, Induced - instrumentation; Hypothermia, Induced - methods; Intensive care medicine; Male; Medical sciences; Neurology; Neuropharmacology; Neuroprotective agent; Pharmacology. Drug treatments; Rats; Rats, Sprague-Dawley; Telemetry; Vascular diseases and vascular malformations of the nervous system
• ISSN: 0271-678X; 1559-7016
• DOI: 10.1038/sj.jcbfm.9600327

Hypothermia reduces cell death and promotes recovery in models of cerebral ischemia, intracerebral hemorrhage and trauma. Clinical studies report significant benefit for treating cardiac arrest and studies are investigating hypothermia for stroke and related conditions. Both local (head) and generalized hypothermia have been used. However, selective brain cooling has fewer side effects than systemic cooling. In this study, we developed a method to induce local (hemispheric) brain hypothermia in rats. The method involves using a small metal coil implanted between the Temporalis muscle and adjacent skull. This coil is then cooled by flushing it with cold water. In our first experiment, we tested whether this method induces focal brain hypothermia in anesthetized rats. Brain temperature was assessed in the ipsilateral cortex and striatum, and contralateral striatum, while body temperature was kept normothermic. Focal, ipsilateral cooling was successfully produced, while the other locations remained normothermic. In the second experiment, we implanted the coil, and brain and body temperature telemetry probes. The coil was connected via overhead swivel to a cold-water source. Brain hypothermia was produced for 24 h, while body temperature remained normothermic. A third experiment measured brain and body temperature along with heart rate and blood pressure. Brain cooling was produced for 24 h without significant alterations in pressure, heart rate or body temperature. In summary, our simple method allows for focal brain hypothermia to be safely induced in anesthetized or conscious rats, and is, therefore, ideally suited to stroke and trauma studies.