Formalin test
Intraplantar injection of formalin evoked a characteristic biphasic licking response. For the control group, the duration of licking in the 1st phase was 48.8±11.7 s, and for the 2nd phase was 141.6±33.0 s. As shown in Figure 2, pre-treatment with different doses of VD, VA or VB had no significant effect against the 1st phase. However, 2nd phase was markedly reduced by VD, with maximal effect observed with 100 mg/kg. VA and VB developed significant effect on the 2nd phase only at doses of 30 and 100 mg/ kg. However, VA effects were lesser pronounced than those of VB or VD. Results obtained demonstrated that VD was the most efficient in reducing the time that the animal spent licking the formalin-injected paw.