Spatially profiling the molecular effects of repetitive transcranial magnetic stimulation in aged rodent brains.

Repetitive transcranial magnetic stimulation (rTMS) is a widely adopted non-invasive tool used to study the brain and as an alternative treatment for neurological disorders. However, the molecular mechanisms affected in the brain regions at and beyond the stimulation site, and how this varies with different rTMS protocols in an aged brain remains unclear. Here we use a combination of bulk RNA-sequencing and spatial transcriptomics to map the molecular changes across a mouse brain in response to two commonly used rTMS protocols: intermittent (iTBS) and continuous theta burst stimulation (cTBS). Wild-type aged (57-72 weeks old), male C57BL/6J mice were treated with a single session of intermittent theta-burst (iTBS), continuous theta-burst (cTBS), or sham stimulation, with four mice used for each stimulation group. Animals were euthanised three hours post-stimulation and the brains were removed and dissected along the midline. Coronal sections from the right brain hemisphere, taken approximately 0.26 - 0.74 mm anterior from bregma, were analysed using spatial transcriptomics.