MicroPET study of brain neuronal metabolism under electrical and mechanical stimulation of the rat tail

Abstract

Small-animal positron emission tomography (microPET) has been widely used for measuring various molecular processes in the rodent brain. The somatotopic projection, however, has not been identified earlier using microPET under electrical stimulation (ES) and mechanical stimulation (MS). This study aimed to utilize microPET to investigate the glucose metabolism of cortical and thalamic responses to ES and MS of the rat tail. The rats were anesthetized by ketamine and a custom-built stereotaxic frame was used to fix the rat head to ensure that the scanned images were concordant with an atlas. [F]-fluorodeoxyglucose (FDG) was used as a radiotracer to reveal the brain metabolic changes. An activation index (AI) was calculated from microPET data o quantify the changes in local metabolic activities normalized to variations in FDG dosage between animals. The results showed that ES increased FDG uptake in both the contralateral thalamus (AI=18) and cortex (AI=12.5), with significant side-to-side differences (P<0.05, paired t-test). MS also significantly increased FDG uptake in both cortical and thalamic regions, although lateralization was absent in the thalamus. This study indicated that microPET can be used to elucidate the functional and quantitative neuronal activities of brain structures of rodents under peripheral stimulation, and could be applied in investigations of brain sensory functions.