TEMPERATURE-DEPENDENT CHANGE OF APPARENT DIFFUSION-COEFFICIENT OF WATER IN NORMAL AND ISCHEMIC BRAIN OF RATS

To identify the temperature dependent change of the apparent diffusion coefficient (ADC) of water in brain tissue, the ADC values of normal rat brain were measured over a range of body temperatures with monitor ing of head temperature using a small water reference implanted under the temporalis muscle. An initial experiment using thermocouples impla nted into the cortex, caudate-putamen, temporalis muscle, and rectum d emonstrated that temperature in all regions were highly correlated ove r a temperature range from 33 to 39 degrees C. In another group of nor mal rats, brain ADC values varied almost uniformly with body temperatu re over the temperature range 33-39 degrees C, implying that brain ADC values accurately reflect changes in brain temperature. The effects o f focal ischemia and administration of the noncompetitive N-methyl-D-a spartate (NMDA) antagonist, CNS-1102, on ADC were also examined, using the suture middle cerebral artery (MCA) occlusion model while maintai ning the body temperature at 37 degrees C. ADC values and therefore br ain temperature in the nonischemic and ischemic hemispheres were not a ffected by the drug. These experiments suggest that brain ADC measurem ent could be useful in animal studies and, potentially, in humans to a ssess the effects of pharmacologic intervention on brain temperature.