Abstract
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Objectives: Up until now, it does not have a clear definition of which brain area responds to pain. Since unbearable pain suffers people in many clinical cases, analgesic becomes valuable to alleviate the unnecessary pain perception. Thus, finding the effective areas of pain processing in brain becomes an important issue in recent years. The present study used the microPET to study brain neuronal activity under peripheral noxious stimuli. Methods: Twelve adult Wistar rats were used in this study. Seven rats was injected 1-1.2 mCi fluorodeoxyglucose (18F-FDG) as a radiotracer, after that they were returned to their cage under minimal surrounding noise for 45 min uptake. Following the uptake, the animals were anesthetized by 1.5% isoflurane and positioned on a stereotaxic holder. Quantitative scanning was then performed by the microPET R4 for 30 min. Formalin studies were executed on the same group after one week; 5% formalin (50 μl) was injected into the left hindpaw following FDG injection. The above protocol was implemented in another five rats and lidocaine (4 mg/kg) was used to suppress the noxious response. In data analysis, images were registered using PMOD and statistical analyses were performed using Matlab. Results: Compare to the baseline data, the local cerebral metabolic rate of glucose in anterior cingulate cortex (ACC) and thalamus (Th) showed significant increase in formalin stimulated animals (p<0.05). The increase of %ID/cc in ACC was from 0.55±0.02 to 0.59±0.02 and Th was from 0.49±0.01 to 0.53±0.01 while somatosensory cortex and hypothalamus did not show obvious increase. Furthermore, radioactivity in ACC and Th was decreased in lidocaine studies. Conclusions: The present study allowed identification of the brain levels involved in pain responses. This should be useful for further evaluation of the effects of new drugs and preclinical therapies for pain.
Research Support (if any): This work was supported by grant nos. NSC-94-2213-E-002-001, NSC-95-3112-B-001-009 and NSC-95-3112-B-001-004 from the National Science Council, Taiwan, ROC.
- Society of Nuclear Medicine, Inc.