Changes in Local Cerebral Glucose Utilization Following Radiofrequency - Induced Local Hyperthermia in the Rat - An Autoradiographic Study

The responsible mechanisms for hyperthermia induced injury in the brain are not fully understood. The changes in glucose metabolism may play an important role in hyperthermia-induced injury. To elucidate these mechanisms, the changes in local cerebral glucose utilization (LCGU) was measured following the induction of localized interstitial hyperthermia using the [^^14 C]-2-deoxy-D-glucose autoradiographic technique. The induction of hyperthermia was achieved by using 8MHz radiofrequency (RF) in rats. The range of hyperthermia is from 37 to 45℃ for 30min. We found that (1) LCGU was significantly decreased in the lesions heated to 45℃; (2) it was increased in the lesions heated to 43℃; and (3) it was increased in the contralateral thalamus and hippocampus of a hyperthermia group. In conclusion, severe hyperthermia at 45℃ caused irreversible cell damage as shown by a marked decrease in LCGU. Hyperthermia at 43℃ caused neuronal shrinkage and an increase in LCGU. In comparison with our previous cerebral blood flow (CBF) study, increased LCGU occurred prior to the oneset of decreased CBF. These findings suggest that the increased LCGU around severely damaged lesions caused by hyperthermia may be manifested as cellular injury and the threshold temperature may be 43℃ for 30min.