Involvement of alpha 1- but not alpha 2-adrenergic systems in the antagonizing effect of paeoniflorin on scopolamine-induced deficit in radial maze performance in rats.

Paeoniflorin, a major constituent of peony root (1 mg/kg, p.o.), attenuated scopolamine-induced deficit in radial maze performance. Both prazosin (0.5 mg/kg, i.p.) and yohimbine (0.3 mg/kg, i.p.) neither impaired radial maze performance by itself nor augmented the scopolamine-induced performance deficit. Prazosin significantly blocked the antagonizing effect of paeoniflorin on the scopolamine deficit, whereas yohimbine did not affect the paeoniflorin effect. These data suggest that the alpha 1-adrenergic but not alpha 2-adrenergic systems are involved in the antagonizing effect of paeoniflorin on the scopolamine deficit in radial maze performance in rats.