Network-targeted Prefrontal Transcranial Magnetic Stimulation (TMS) in Neurodegenerative and Neuropsychiatric Disorders

d-cycloserine (DCS), an NMDA receptor partial agonist vs. placebo on motor evoked potentials (MEPs) before and after 300 pulses (1.5 sec on/ 58.5 sec off) of 10 Hz rTMS over the left motor cortex at 80% motor threshold. Baseline MEP measures were taken 1 hour after drug administration to account for effects on baseline excitability, rTMS was then administered 2 hours after drug, and post-TMS measures were obtained every 15 minutes for 1 hour following rTMS. Results: Averaged normalized MEPs over the time course were higher when participants received DCS than placebo, with an overall increase in least squares means from 1.27 (placebo) to 1.55 (DCS), difference of 0.29, standard error 0.14 (F1⁄44.48, df1⁄462; p1⁄40.038). Baseline data (raw values) were not significantly different per student’s two-tailed paired t-test, placebo 1.129 mV; DCS 0.956 mV; p1⁄40.173. Conclusions: Consistent with our hypothesis that 10 Hz rTMS may work through LTP, a modest, but significant, potentiating effect of d-cycloserine was observed onMEPs after 10 Hz rTMS. This pilot data highlights the need for larger mechanistic studies. Conflicts of Interests: None. Funding: This work was supported by the National Institutes of Health (NIDA), MUSC (DART) training grant #: R25DA020537. v