Cerebral glucose metabolism changes in rat brain upon forepaw electrical stimulation at different frequencies

PET imaging techniques and statistical parametric mapping analysis have been developed to identify neuronal functional activation from brain imaging. The purpose of this study was to examine the efficacy of the glucose metabolism in rat brain during forepaw electrical stimulation with different frequencies (3, 10, or 20 Hz) compared with a nonstimulated group (control). Fluorine-18 fluorodeoxyglucose was injected after confirmation of the range of normal physiology. For quantitative analysis, we used cerebral metabolism rate of glucose consumption (CMRglc) responses in the primary somatosensory cortex (S1FL) and motor cortex (M1). On comparing CMRglc responses in the contralateral S1FL and M1 with those of the ipsilateral areas in intragroup analysis, a significant increase (P<0.05) was observed in two electrical stimulation groups (10 and 20 Hz) but not at the 3 Hz level. In intergroup analysis, the CMRglc responses in the contralateral region of interest were compared with those of the control group to validate which electrical frequency conditions were appropriate to induce neuronal functional activation. Among the stimulation groups, significant increases in CMRglc response were only observed at 10 Hz (P<0.05). Therefore, 10 Hz is the most suitable frequency to confirm changes in CMRglc in the S1FL and M1 of the rat brain, and also fluorine-18 fluorodeoxyglucose PET could be useful to investigate recovery and plasticity in neurological diseases associated with primary sensory-motor cortex function.