Spasmolytic activity of Aquilariae Lignum Resinatum extract on gastrointestinal motility involves muscarinic receptors, calcium channels and NO release.

Aquilariae Lignum Resinatum (ALR), the dry rhizome of Aquilaria agallocha R. (Thymelaeaeeae), has been widely used to treat emesis, stomachache and gastrointestinal dysfunction.This study evaluates the effects of ALR methanol extract on gastrointestinal motility (GIM) and possible mechanisms of the action involved.

In vivo, the study evaluated the effects of ALR (200-800 mg/kg) on gastric emptying and small intestinal motility in normal and neostigmine-induced adult KM mice. The in vitro effects of ALR (0.2-1.6 mg/mL) on GIM were performed on isolated jejunum of Wistar rats, pretreated with acetylcholine (ACh), KCl, CaCl₂, and pre-incubation with l-NAME (a selective inhibitor of the nitric oxide synthase).

In vivo, ALR (800 mg/kg) decreased gastric emptying (70.82 ± 9.81%, p < 0.01, compared with neostigmine group 91.40 ± 7.81%), small intestinal transit (42.82 ± 3.82%, p < 0.01, compared with neostigmine group 85.53 ± 5.57%). In vitro, ALR concentration dependently decreased the contractions induced by ACh (10^-5 M) and KCl (60 mM) with respective EC₅₀ values of 0.35 and 0.32 mg/mL. The Ca²⁺ concentration-response curves were shifted by ALR to the right, similar to that caused by verapamil (the positive). The spasmolytic activity of ALR was inhibited by pre-incubation with l-NAME.

ALR played a spasmolytic role in GIM, which is probably mediated through inhibition of muscarinic receptors, blockade of Ca²⁺ influx and NO release. This is the first study presenting a comprehensive description of the effects of ALR on GIM.