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Pharmacol Biochem Behav. 2012 Apr;101(2):217-21. doi: 10.1016/j.pbb.2012.01.011. Epub 2012 Jan 21.

L-theanine partially counteracts caffeine-induced sleep disturbances in rats.

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Department of Pharmacology, School of Medicine, Kyungpook National University, 2-101 Dongin-dong, Jung-gu Daegu 700-422, Republic of Korea.


L-theanine has been reported to inhibit the excitatory effects of caffeine. The present study examined the effects of L-theanine on caffeine-induced sleep disturbances in rats. Rats received the following drug pairings: saline and saline (Control), 7.5 mg/kg caffeine and saline, or 7.5 mg/kg of caffeine followed by various doses of L-theanine (22.5, 37.5, 75, or 150 mg/kg). Vigilance states were divided into: wakefulness (W), transition to slow-wave sleep (tSWS), slow-wave sleep (SWS), and rapid-eye-movement sleep (REMS). Caffeine significantly increased the duration of W and decreased the duration of SWS and REMS compared to the Control. Although L-theanine failed to reverse the caffeine-induced W increase, at 22.5 and 37.5 mg/kg (but not at 75 and 150 mg/kg), it significantly reversed caffeine-induced decreases in SWS. In conclusion, low doses of L-theanine can partially reverse caffeine-induced reductions in SWS; however, effects of L-theanine on caffeine-induced insomnia do not appear to increase dose-dependently.

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