The anxiolytic activity of calcium channel antagonists in experimental models of anxiety in rats

Objective: To evaluate the anxiolytic-like behavioural effects of four calcium channel antagonists (CCAs) belonging to different classes in rats. Methods: Study was conducted using male Wistar strain albino rats in two non-conflicting models, elevated plus maze and light-dark arena. CCAs like verapamil (5, 10 and 20 mg/kg), diltiazem (5, 10 and 20 mg/kg), nifedipine (2.5, 5 and 10 mg/kg), flunarizine (5, 10 and 20 mg/kg) and the standard anxiolytic diazepam (0.25, 0.5 and 1 mg/kg) were administered intraperitoneally 30 minutes prior to the testing. Results: Verapamil (5 and 10 mg/kg), diltiazem (10 and 20 mg/kg) and flunarizine (5 and 10 mg/kg) increased the number of entries into, time spent and the number of rears in the light arena of the light-dark arena model. Only verapamil (5 mg/kg) and diltiazem (10 and 20 mg/kg) increased the number of open arm entries, percentage ratio of open/total arm entries and percentage of time spent in open arms in elevated plus model. These changes are similar to that produced by the standard anxiolytic diazepam (0.5 and 1 mg/kg). On the other hand, nifedipine had no effect on either of the test models. Conclusion: Among the CCAs tested only verapamil, diltiazem and flunarizine have anxiolytic-like activity comparable to diazepam.