Results: 1) PPL could dose-dependently raise the pain threshold in tail stimulation-vocalization test in rats and inhibit the writhing reaction induced by acetic acid in mice.

• 方法：采用扭体法、电刺激鼠尾-嘶叫法、钾离子透入法和辐射热-缩腿法等行为学指标以及丘脑束旁核神经元对伤害性刺激的放电反应的电生理指标。