Interactions of verapamil and diltiazem with ketamine: effects on memory and sleeping time in mice.

The effects of ketamine (3, 10 and 30 mg/kg) alone and in combination with verapamil (10 mg/kg) or diltiazem (30 mg/kg) on the acquisition, consolidation and retrieval of memory using a passive avoidance task in mice were studied. Ketamine significantly inhibited the acquisition and consolidation of memory at 10 and 30 mg/kg dose levels and these effects were antagonized by diltiazem 30 mg/kg but not by verapamil 10 mg/kg. Studies of sleeping time demonstrated that pretreatment with verapamil 10 mg/kg increased the duration of sleeping time. Diltiazem, however, did not potentiate the effects of ketamine on sleeping time. The present findings indicate that diltiazem can counter the effects of ketamine on memory. The data also indicates that pretreatment of surgical patients with verapamil may reduce the dose of ketamine required for anesthesia.