Mouse body weights are shown as % body weight change and expressed as mean ± S.E.M. for n=8 mice per treatment group and are representative of two independent experiments. Mice were treated with matrine (100 mg.kg⁻¹) or vehicle (saline) by oral gavage 1 h before the first daily CS exposure. Two-way ANOVA with Sidak post-hoc test was performed to assess statistical significance **P<0.01, compared with sham+vehicle mice.