GABAergics & Anxiolytics — References

Mirrored Reference Dossier

Parent Topic: GABAergics & Anxiolytics | References Hub: 02 - Compounds & Molecules References MOC

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Landmark Peer-Reviewed Studies

1. Kimura et al. (2007) — Biological Psychology

• Citation: Kimura, K., Ozeki, M., Juneja, L. R., & Ohira, H. (2007). L-Theanine reduces psychological and physiological stress responses. Biological Psychology, 74(1), 39–45.
• Identifiers: PMID: 16930802 (PubMed · Europe PMC) | DOI: 10.1016/j.biopsycho.2006.06.006 (DOI · SciDB · Scholar)
• Study Design & Sample Size: Randomized, double-blind, placebo-controlled 4-way crossover trial in healthy adults ($N=12$) subjected to an acute mental arithmetic stress task.
• Key Quantitative Outcomes: Oral ingestion of $200\text{ mg}$ L-Theanine significantly attenuated the acute stress-induced rise in heart rate ($p<0.05$), suppressed salivary immunoglobulin A (s-IgA) reactivity ($p<0.05$), reduced subjective State-Trait Anxiety Inventory (STAI) scores ($p<0.01$), and suppressed the sympathetic low-frequency to high-frequency ($\text{LF/HF}$) heart rate variability ratio ($p<0.05$) compared to placebo.

2. Owen et al. (2008) — Nutritional Neuroscience

• Citation: Owen, G. N., Parnell, H., De Bruin, E. A., & Rycroft, J. A. (2008). The combined effects of L-theanine and caffeine on cognitive performance and mood. Nutritional Neuroscience, 11(4), 193–198.
• Identifiers: PMID: 18681988 (PubMed · Europe PMC) | DOI: 10.1179/147683008X301513 (DOI · SciDB · Scholar)
• Study Design & Sample Size: Randomized, double-blind, placebo-controlled crossover trial in healthy human volunteers ($N=27$) comparing $50\text{ mg}$ caffeine alone vs. $50\text{ mg}$ caffeine + $100\text{ mg}$ L-Theanine ($1:2$ ratio) vs. placebo at $60\text{ and }90\text{ minutes}$ post-ingestion.
• Key Quantitative Outcomes: The L-Theanine + Caffeine combination significantly improved both reaction time speed and accuracy on an attention-switching task at $60\text{ min}$ ($p<0.01$) and significantly reduced susceptibility to distracting information on a memory task at both $60\text{ and }90\text{ min}$ ($p<0.05$), outperforming caffeine monotherapy.

3. Nobre et al. (2008) — Asia Pacific Journal of Clinical Nutrition

• Citation: Nobre, A. C., Rao, A., & Owen, G. N. (2008). L-theanine, a natural constituent in tea, and its effect on mental state. Asia Pacific Journal of Clinical Nutrition, 17(Suppl 1), 167–168.
• Identifiers: PMID: 18296328 (PubMed · Europe PMC) | Google Scholar ID: Nobre2008LTheanineEEG
• Study Design & Sample Size: Quantitative electroencephalography (qEEG) randomized crossover study in healthy resting humans ($N=35$) at $45,60,75,90,\text{and }105\text{ minutes}$ after ingesting $50\text{ mg}$ L-Theanine vs. water control.
• Key Quantitative Outcomes: A physiological dose of $50\text{ mg}$ L-Theanine produced a linear, statistically significant increase in $8\text{–}13\text{ Hz}$ Alpha-band EEG spectral power across parietal and occipital cortices ($p<0.05$), establishing cortical alpha synchronization without drowsiness.

4. Awad et al. (2009) — Phytotherapy Research

• Citation: Awad, R., Muhammad, A., Durst, T., Trudeau, V. L., & Arnason, J. T. (2009). Bioassay-guided fractionation of lemon balm (Melissa officinalis L.) using an in vitro measure of GABA transaminase activity. Phytotherapy Research, 23(8), 1075–1081.
• Identifiers: PMID: 19165747 (PubMed · Europe PMC) | DOI: 10.1002/ptr.2712 (DOI · SciDB · Scholar)
• Study Design & Sample Size: Biochemical enzymatic assay and phytochemical fractionation of Melissa officinalis on rat brain GABA Transaminase (GABA-T) and Glutamic Acid Decarboxylase (GAD).
• Key Quantitative Outcomes: Demonstrated that Melissa officinalis extract and its primary constituent rosmarinic acid potently inhibit GABA Transaminase (GABA-T) with an ${\text{IC}}_{50}=0.35\text{ mg/mL}$ ($40\%$ inhibition by rosmarinic acid at $100\mu \text{g/mL}$, $p<0.01$), preventing the catabolic breakdown of synaptic GABA.