Effect of Choto-san, a kampo medicine, on impairment of passive avoidance performance in mice.

In mice with procephalic ischaemia loading, disrupted passive avoidance retention performance was dose-dependently improved by Choto-san, but this effect was antagonized by NAN-190, a serotonin1A receptor antagonist. In mice with decreased intracerebral serotonin concentration, Choto-san prevented disturbance in acquiring a passive avoidance response after scopolamine administration, but did not influence the decreased serotonin concentration. These results suggested that Choto-san showed the anti-amnestic effect based on the stimulation of serotonin1A receptors.