The methanol (MeOH) extracts from 36 crude drugs or medicinal plants were investigated for their effects on [3H]spiperone-binding to membrane preparation from rat brain. The MeOH extracts of Amsonia elliptica or Corydalis Tubur or Evodia Fructus showed a strong inhibitory effect of [3H]spiperone-binding to D-2 receptors of membrane fraction from rat brain. The activity of MeOH extracts of these drugs transferred to the alkaloid fraction, while main alkaloids of each medicinal plant or crude drug, for example, β-yohimbine, corydaline, evodiamine, synephrine, could not show high actibity, respectively. Thus, these results suggest that inhibition by these medicinal plants may be due to another components in the alkaloid fraction.
