Background: Glycyrrhiza glabra (Licorice) has been traditionally used as a medicinal plant in Iran for treatment of diseases such as gastric ulcer and relieve intestinal spasms.

Objective: In the present study, the effect of hydro-alcoholic extract of licorice rhizome on mechanical activity of isolated colon of male rats has been studied.

Methods: In this experimental study, the colon tissue of 10 adult male rats were dissected and separated into two groups: experimental and control. Each group including ten strips of tissue. The segments were connected to a force transducer longitudinally and inserted to an organ bathe contained oxygenated Tyrode solution (37 °C, pH=7.4). Their mechanical activity were recorded by power lab AD instrument in basal condition, and after administration of acetylcholine (4×10^-6M) and Atropine (10^-6M) in the presence and absence of licorice rhizome extract (0.036 mg/ml). Also, the mechanical activity of control group segments were recorded at the same condition with extract solvent (ethanol %70).

Results: A significant decrease in mechanical activity was found after administration of hydro-alcoholic extract of licorice compared with the control group. Also, a significant decrease of mechanical activity was seen in the presence of extract and acetylcholine compared to the control group. While the mechanical activity of tissue didn’t significant changed in the presence of Atropine and extract between experimental and control groups.

Conclusion: We can conclude that hydro-alcoholic extract of licorice has modifying effect on colon motility, and this activity maybe occurred independent of the cholinergic system.