One strategy to understand bipolar disorder is to study the mechanism of action of mood-stabilizing drugs, such as valproic acid and lithium. This approach has implicated a number of intracellular signalling elements, such as GSK3β (glycogen synthase kinase 3β), ERK (extracellular-signal-regulated kinase)/MAPK (mitogen-activated protein kinase) or protein kinase C. However, lamotrigine does not seem to modulate any of these targets, which is intriguing given that its profile in the clinic differs from that of valproic acid or lithium, with greater efficacy to prevent episodes of depression than mania. The primary target of lamotrigine is the voltage-gated sodium channel, but it is unclear why inhibition of these channels might confer antidepressant efficacy. In healthy volunteers, we found that lamotrigine had a facilitatory effect on the BOLD (blood-oxygen-level-dependent) response to TMS (transcranial magnetic stimulation) of the prefrontal cortex. This effect was in contrast with an inhibitory effect of lamotrigine when TMS was applied over the motor cortex. In a follow-up study, a similar prefrontal specific facilitatory effect was observed in a larger cohort of healthy subjects, whereas valproic acid inhibited motor and prefrontal cortical TMS-induced BOLD response. In vitro, we found that lamotrigine (3–10 μM) enhanced the power of gamma frequency network oscillations induced by kainic acid in the rat hippocampus, an effect that was not observed with valproic acid (100 μM). These data suggest that lamotrigine has a positive effect on corticolimbic network function that may differentiate it from other mood stabilizers. The results are also consistent with the notion of corticolimbic network dysfunction in bipolar disorder.
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Conference Article|
September 21 2009
Neural network dysfunction in bipolar depression: clues from the efficacy of lamotrigine
Charles H. Large;
Charles H. Large
1
*Neurosciences Centre of Excellence for Drug Discovery, Medicines Research Centre, GlaxoSmithKline S.p.A., Via Fleming 4, 37135 Verona, Italy
1To whom correspondence should be addressed (email charles.h.large@gsk.com).
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Elena Di Daniel;
Elena Di Daniel
†Neurosciences Centre of Excellence for Drug Discovery, GlaxoSmithKline, New Frontiers Science Park, Third Avenue, Harlow, Essex CM19 5AW, U.K.
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Xingbao Li;
Xingbao Li
‡Brain Stimulation Laboratory, Medical University of South Carolina, 67 President St., Room 502 North, PO Box 250861, Charleston, SC 29425, U.S.A.
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Mark S. George
Mark S. George
‡Brain Stimulation Laboratory, Medical University of South Carolina, 67 President St., Room 502 North, PO Box 250861, Charleston, SC 29425, U.S.A.
§Ralph H. Johnson Veterans Administration Hospital, 109 Bee Street, Charleston, SC 29401, U.S.A.
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Publisher: Portland Press Ltd
Received:
April 06 2009
Online ISSN: 1470-8752
Print ISSN: 0300-5127
© The Authors Journal compilation © 2009 Biochemical Society
2009
Biochem Soc Trans (2009) 37 (5): 1080–1084.
Article history
Received:
April 06 2009
Citation
Charles H. Large, Elena Di Daniel, Xingbao Li, Mark S. George; Neural network dysfunction in bipolar depression: clues from the efficacy of lamotrigine. Biochem Soc Trans 1 October 2009; 37 (5): 1080–1084. doi: https://doi.org/10.1042/BST0371080
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