Abstract
Paeoniflorin, a major constituent of peony root, has been demonstrated to attenuate the radial maze performance deficit produced by scopolamine. In the present study, to investigate the possible involvement of β-adrenergic systems in the paeoniflorin antagonism of the scopolamine deficit, the effects of two β-adrenoceptor antagonists, propranolol and atenolol, on the paeoniflorin effect were examined in male Wistar rats. Paeoniflorin (1 mg/kg, p.o.) significantly attenuated the scopolamine HBr (0.3 mg/kg, i.p.)-induced deficit in the choice accuracy in radial maze performance without changing the running time prolonged by scopolamine. Neither D, L-propranolol HCl, a lipophilic β-antagonist, at 3 mg/kg, i.p. nor atenolol, a hydrophilic β1-antagonist that is known to hardly ever cross the blood-brain barrier, at 1 mg/kg, i.p. impaired maze performance by itself or aggravated the scopolamine-induced deficit in radial maze performance. Both antagonists, however, completely blocked the antagonizing effect of paeoniflorin on the scopolamine deficit. These data suggest that the β-adrenergic systems, especially peripheral β1-adrenergic systems, are involved in the antagonizing effect of paeoniflorin on the scopolamine deficit in radial maze performance in rats.
