Effects of single-dose L-theanine on motor cortex excitability

Shiwen Yuan, Joshua C Brown, Michael Gold, Eric Tirrell, Richard N Jones, Linda L Carpenter, Shiwen Yuan, Joshua C Brown, Michael Gold, Eric Tirrell, Richard N Jones, Linda L Carpenter

No abstract available

Keywords: Brain Excitability; GABA; L-Theanine; NMDA.

Conflict of interest statement

Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Figures

Fig. 1.

The Effects of L-Theanine on Motor Cortex Intracortical Excitability Measured by SICI, ICF and LICI. (A) Study Design. (B–D) Comparison between pre-to-post-drug SICI change (ΔSICI), ICF change (ΔICF) and LICI change (ΔLICI), respectively under L-theanine Condition and Placebo Condition. Mean ± SE ΔSICIL-theanine = 0.059 ± 0.028 vs. ΔSICIPlacebo = 0.005 ± 0.060, p = 0.450, Cohen’s d = 0.35. The black lines connect the same subjects between two conditions. The orange line represents mean ΔSICI under L-theanine condition and placebo condition. Mean ± SE ΔICFL-theanine = 0.073 ± 0.073 vs. ΔICFPlacebo = −0.341 ± 0.176, *p = 0.016, Cohen’s d = 1.02. The black lines connect the same subjects between two conditions. The blue line represents mean ΔICF under L-theanine condition and placebo condition. Mean ± SE ΔLICIL-theanine = 0.145 ± 0.100 vs. ΔLICIPlacebo = −0.068 ± 0.053, *p = 0.037, Cohen’s d = 0.91. The black lines connect the same subjects between two conditions. The red line represents mean ΔLICI under L-theanine condition and placebo condition. Δ value > 0 means an increase in SICI, ICF or LICI value; Δ value < 0 means a decrease in SICI, ICF or LICI value. Note that an increase in ICF value indicates enhanced NMDA-R mediated intracortical facilitation; whereas an increase in SICI or LICI value indicates attenuation of GABAA-R or GABAB-R mediated intracortical inhibition, respectively. Abbreviations: ppTMS = Paired-pulse Transcranial Magnetic Stimulation, SICI = Short-interval Intracortical Inhibition, ICF = Intracortical Facilitation, LICI = Long-interval Intracortical Inhibition, SE = Standard Error of the Mean, NMDA-R = N-methyl-D-aspartate receptor, GABAB-R = γ-aminobutyric acid-B receptor.