The impact of repetitive transcranial magnetic stimulation on locomotion and brain metabolism: an [18F]FDG PET study in rats

Repetitive transcranial magnetic stimulation (rTMS) is a non-invasive neurophysiological technique used to modulate brain activity and has emerged as a novel treatment for various neurological and psychiatric disorders. The neuronal effects of rTMS, particularly its influence on brain glucose metabolism, remain an area of ongoing research. This study aims to characterize the impact of rTMS on brain glucose uptake using 2-deoxy-2-[(18) F]fluoro-D-glucose ([(18) F]FDG) PET imaging and spontaneous motor activity in healthy rats after 14 consecutive days of daily stimulation. A figure-eight coil designed for rodents delivered rTMS at 5 Hz for 10 min/day. The effects of rTMS in 16 healthy Wistar rats were assessed (8 sham-stimulated and 8 rTMS-treated) through an open field test and [F-18]FDG microPET imaging. Standardized uptake values (SUV) were calculated to quantify glucose uptake. Results showed no significant effects on motor activity or anxiety-like behavior as assessed in the open field test. However, rTMS induced a significant decrease in [(18) F]FDG uptake in nine cortical regions, as well as in the amygdala, medial geniculate nucleus, and superior colliculus (p < 0.05). MicroPET analysis revealed that 5 Hz rTMS inhibited glucose metabolism in cortical and subcortical brain regions. Notably, no clear correlation was found between rTMS-induced changes in brain activity and the spontaneous behaviors observed during the open field test. These findings suggest that high-frequency rTMS can induce inhibition of brain activity.