Anxiolytic Effects of Acute Injection of Hydro-Alcoholic Extract of Lettuce in the Elevated Plus-Maze Task in Rats

Anxiety is a physiological state characterized by cognitive, somatic, emotional, and behavioral components. There is some evidence in traditional medicine for the effectiveness of lettuce (Lactuca sativa) in the treatment of anxiety in humans. The present study investigated the effects of a hydro-alcoholic extract of lettuce on rat behavior in the elevated plus-maze (EPM) and the results compared with the effects of diazepam. Adult male Wistar rats weighing 200 – 240 g were used in the present study. Seven different groups of rats received an intraperitoneal (IP) injection of lettuce extract (50, 100, 200 mg/kg), diazepam (0.3, 0.6, or 1.2 mg/kg), or vehicle (control group), 30 minutes before entering the EPM test. The total distance covered by the animals, the percentage of entries into the open arms of the EPM, the time spent in the open arms, and the number of entries into the closed arms were recorded for a 5 minutes duration. An IP injection of both diazepam and lettuce extract before an EPM trial significantly increased the percentage of open arm entries and the time spent in the open arms. Diazepam decreased the total distance covered by the animals and the number of closed arm entries, whereas lettuce extract had no effect on these parameters. Locomotor activity was not significantly changed by the lettuce extract. Acute administration of lettuce extract has an anxiolytic profile in rats similar to that of anxiolytic diazepam at low dose. Future investigations are essential for better understanding of the anxiolytic properties and neurobiological mechanisms of lettuce extract.