BAY K 8644 enhances immobility in the mouse behavioral despair test, an effect blocked by nifedipine.

The effect of the dihydropyridine calcium channel agonist, BAY K 8644 (0.05, 0.1, 0.5 mg/kg i.p.), in the mouse behavioral despair test was investigated. BAY K 8644 dose dependently prolonged the duration of immobility. The BAY K 8644 (0.1 mg/kg)-induced prolongation of immobility was antagonized by the dihydropyridine calcium channel antagonist, nifedipine, but not by the non-dihydropyridine type antagonists, verapamil and diltiazem. The effect of BAY K 8644 was also antagonized by desipramine and imipramine but not by citalopram and iprindole. Therefore we suggest that central dihydropyridine binding sites play a role in despair behavior.