tokens: For each of the three tested calcium channel blockers ( diltiazem , verapamil and bepridil ) 6 groups of mice were treated by two different doses , i . e . 2 and 10 mg / kg / i . p . , or an equal volume of saline for the control group ( n = 20 ) ; 15 minutes later , all the animals were injected with a single 50 mg / kg / i . p . dose of bupivacaine .