Effect of withdrawal from long-term nifedipine administration on open-field habituation in the rat

The effects of withdrawal from long-term administration of nifedipine (2.5 mg/kg, ip, twice daily for 30 days) on open-field habituation were evaluated in 3-month old male Wistar rats (13-14 animals per group). Habituation was evaluated by the ratio between locomotion or rearing frequencies obtained in the second and the first open-field session for each animal. Nifedipine treatment did not modify the locomotion ratio (with a mean +/- SEM ratio of 0.66 +/- 0.12 for control and 0.45 +/- 0.08 for nifedipine-treated group) nor the rearing ratio (with a mean +/- SEM ratio of 0.51 +/- 0.12 for control and 0.62 +/- 0.18 for nifedipine-treated group). The possible factors underlying the discrepancy between the present results and the commonly reported positive effects of calcium channel blockers on memory are discussed.