Effects of lamotrigine on human motor cortex plasticity

Area of Science:

• Neuroscience
• Psychopharmacology

Background:

• Lamotrigine (LTG) is an anticonvulsant also used as a mood stabilizer.
• Mood disorders may involve impaired neuronal plasticity, including long-term potentiation (LTP) and long-term depression (LTD).
• The precise effects of LTG on human neuronal plasticity are not fully understood.

Purpose of the Study:

• To investigate the impact of a single oral dose of LTG (300 mg) on motor cortical plasticity in healthy adults.
• To determine if LTG modulates plasticity differently based on an individual's baseline response to plasticity-inducing stimulation.

Main Methods:

• A placebo-controlled, randomized, double-blind crossover study involving 26 healthy adults.
• Paired associative stimulation (PAS(25)) was used to induce LTP-like plasticity.
• Motor evoked potential (MEP) amplitudes were measured before and after PAS(25) to assess plasticity.

Main Results:

• LTG significantly reduced the LTP-like increase in MEP amplitudes in individuals prone to LTP.
• LTG also reduced the LTD-like decrease in MEP amplitudes in individuals prone to LTD, with some showing an MEP increase.
• These findings indicate LTG differentially modulates cortical plasticity based on individual response.

Conclusions:

• LTG differentially modulates non-invasively stimulated cortical plasticity in humans.
• The drug's effects depend on an individual's intrinsic capacity for LTP-like or LTD-like plasticity.
• This modulation may underlie LTG's efficacy in epilepsy and mood disorders by downregulating excessive LTP or LTD.