Anxiolytic Effects of L-Theanine: A Component of Green Tea, when Combined with Midazolam, in the Male Sprague-Dawley Rat

Tuesday, 13 July 2010: 1:45 PM

Thomas E. Ceremuga, BA, BSN, MSN, PhD
Graduate School, Academy of Health Sciences, AMEDDC&S, US Army Graduate Program in Anesthesia Nursing, Fort Sam Houston, TX

Learning Objective 1: discuss the hypothesis of the study: Does the green tea compound, L-theanine, have anxiolytic effects in the laboratory rat?

Learning Objective 2: describe the findings of the study that L-theanine combined with midazolam significantly decreased anxiety, motor movements, and locomotion.

Purpose: The purpose of this study was to determine if the green tea compound, L-theanine, has anxiolytic effects in the laboratory rat.  Additionally the study investigated the effects of L-theanine at the GABAA receptor in the central nervous system.  The research questions were: 1) Does L-theanine (a green tea compound) have anxiolytic effects in the laboratory rat? and 2) if there is an anxiolytic effect, is the anxiolytic effect of L-theanine a result of modulation of the benzodiazepine site on the GABAA receptor?

Methods: A five group prospective study using an experimental between groups design was used. Fifty-five rats were divided into five groups: control; L-theanine; midazolam (positive control); flumazenil plus L-theanine; and midazolam plus L-theanine. The behavioral component of anxiety was evaluated using the elevated plus maze.  Data analysis was performed using a two-tailed Multivariate Analysis of Variance (MANOVA) and Sheffe post-hoc test.

Results: Data suggest that L-theanine does not produce anxiolysis by modulation of the GABAA receptor; however, in combination with midazolam, a synergistic or additive effect was demonstrated by decreased anxiety, motor movements and locomotion.

Conclusion: L-theanine may affect anxiety and movement.  Future experiments should explore anxiolytic and motor effects of L-theanine using other balance and locomotion instruments such as the rotorod.  Additional studies might include investigating the effects of L-theanine at glutamatergic receptors and at the neuromuscular junction.  As evidenced by this research, the use of herbals such as L-theanine (a green tea compound) may have important interactions with other medications (e.g., midazolam) and may result in significant adverse effects.  These data may provide direction for further studies examining L-theanine and its effects on anxiety and motor activity, a concern for healthcare providers whose patients are consuming green tea.