To investigate different cortical effects of lamotrigine and valproic acid, 30 paid healthy adult men were given, in a randomized/blinded fashion on three separate days (separated by a week), either a single dose of lamotrigine 325 mg, or a single dose of valproic acid 1,250 mg, or placebo. Resting motor threshold (RMT), cortical silent period (CSP) and motor evoked potential recruitment curves (RC) were assessed at baseline and 3 h after administration of each medication (or placebo). Lamotrigine caused a significant increase (63.32 vs. 69.25) in the RMT, compared with an insignificant increase following valproic acid (62.50 vs. 63.35), and a decrease (62.60 vs. 62.36) following placebo (F 2,26 = 18.58, P < 0.0001). No significant difference in CSP was found between placebo and drugs (F 2,26 = 0.119, P > 0.05). RCs were significantly suppressed by lamotrigine (t = 2.07, P < 0.05) and enhanced by valproic acid (t = 2.39, P < 0.05). Lamotrigine and valproic acid have different effects on cortical neuronal excitability as demonstrated by TMS.
Bibliographical noteFunding Information:
The authors would like to thank Dr Jeffrey Borckardt for running HLM analysis. This study was funded primarily by an unrestricted research grant from GlaxoSmithKline to Dr George, as well as from Center for Advanced Imaging Research and Brain Stimulation Laboratory infrastructure and resources. CHL is a full-time employee of GlaxoSmithKline S.p.A. None of the other authors have equity or financial conflicts. Drs Li and George had full access to all of the data in the study and take responsibility for the integrity of the data and the accuracy of the data analysis. Presented in abstract form at the annual meeting of American College of Neuropsychopharmacology, Hollywood, FL, USA, December 14, 2006 and the annual meeting of the Society of Biological Psychiatry, San Diego, CA, USA, May 21, 2007.
- Motorcortical excitability
- Transcranial magnetic stimulation
- Valproic acid