Effects of L-theanine on Motor Cortex Excitability in Healthy Subjects: A Paired-Pulse TMS Study

• Status: Completed
• Trial end date: 2021-05-31
• Target enrollment: 0
• Participant gender: All

Summary

Major depressive disorder (MDD) is a serious mental illness and the leading cause of disability worldwide. New pharmacotherapeutic agents with complementary neurobiological mechanism and better side effect profile are of great needs. In addition to the monoamine system, the glutamatergic system plays a crucial role in MDD.

L-theanine (N5-ethyl-L-glutamine) is the primary psychoactive component uniquely in green tea. Preclinical studies have demonstrated anti-depressant effect of L-theanine in rodents and provided evidences for its pharmacological properties of N-methyl-D-aspartate (NMDA) and gamma-aminobutyric acid (GABA) agonism. Yet these effects have not been proven in humans. Only one open-label clinical trial has studied and supported antidepressant effects of L-theanine in MDD patients. We propose using pair-pulse transcranial magnetic stimulation (ppTMS) to probe how L-theanine may manipulate the glutamatergic and GABA systems in the frontal region by changing cortical excitability first in healthy subjects. We plan to investigate the neurobiological effects of L-theanine in healthy subjects first.

Granted that the first phase pilot trial provides neurophysiological evidence of L-theanine on motor cortex excitability in human subjects, next phases of studies on L-theanine in MDD patients cortical excitability could be justified.

• Phase: Early Phase 1
• Accepts Healthy Volunteers?: Accepts Healthy Volunteers

Details

• Lead Sponsor: Butler Hospital

Criteria

Inclusion Criteria:

1. Adult, aged between 18 and 65 years old;

2. Able to read/speak English and give informed consent

3. No current or history of Axis I psychiatric disorders by DSM-5.

4. Free of psychotropic medication use

Exclusion Criteria:

1. History of significant acute or chronic neurological or medical disorder or condition that increases risk for seizure with TMS;

2. History of alcohol use disorder, nicotine dependence, adjustment disorder;

3. History of allergic reactions to L-theanine or green tea;

4. Pregnancy;

5. Unable/unwilling to abstain from nutraceutical supplements and psychotropic agents during participation in the study

6. Unable/ unwillingness to refrain from recreational substance use (e.g. alcohol or marijuana) during participation in the study;

7. Meet criteria for exclusion from TMS or MRI procedures, including intracranial metal implants or nonremovable ferromagnetic items in the head/neck.