Central inhibitory effects of water extract of Acori graminei rhizoma in mice

Abstract

The present study evaluated in mice the central inhibitory effects of a water extract of shichangpu (Acori graminei rhizoma (AGR), the dry rhizome of Acorus gramineus Soland. (Araceae)). AGR (0.5–5.0 g/kg) dose-dependently decreased the locomotor activity and increased the pentobarbital-induced sleeping time, but had no significant effect on the treadmill performance. AGR also dose-dependently inhibited the intensity of apomorphine-induced stereotypic behavior. At the highest dose (5.0 g/kg), AGR had a weak anticonvulsant effect on the pentylenetetrazol-induced seizures. Receptor binding assays showed that AGR competed with [ 3H]SCH-23390 and [ 3H]YM-09151-2 for specific binding to striatal dopamine D 1 and D 2 receptors with K i values of 5.6 and 4.2 mg/ml, respectively. AGR also competed with [ 3H]muscimol for specific binding to the γ-aminobutyric acid (GABA) binding site of cortex GABA A receptors with a K i value of 0.31 mg/ml. It also increased the specific binding of [ 3H]flunitrazepam to the benzodiazepine binding site of the GABA A receptors, suggesting a GABA agonist-like action. These results suggested that the central inhibitory effects of AGR were probably effected through an action on the central dopamine receptors and GABA A receptors. The principle of AGR acting at these ligand binding sites was not α-asarone, one of the important principles of AGR, since that α-asarone (10 −6–10 −4 M) had no significant interactions with these binding sites.