Figure. 1.

Cumulative number of spontaneous withdrawal signs observed in morphine-dependent monkeys at 30, 60, 90, 120, and 150 min after receiving a subcutaneous injection of vehicle, L-theanine (1.0, 4.0, or 8.0 mg/kg), or morphine sulfate (4.0 mg/kg). * p < 0.05, ** p < 0.01, indicate significant differences from vehicle-treatment at each specific time point; Data are shown as the mean ± SEM, N = 4 monkeys/group for each dose of L-theanine; N = 7 monkeys for morphine treatment; N = 6 monkeys for vehicle treatment.