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

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 lime, 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 [H-3]SCH-23390 and [H-3]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 [H-3]muscimol for specific binding to the gamma-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 [H-3]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 alpha-asarone, one of the important principles of AGR, since that alpha-asarone (10(-6)-10(-4) M) had no significant interactions with these binding sites. (C) 1998 Elsevier Science Ireland Ltd. All rights reserved.