Blockade by nifedipine of repeated restraint stress-induced delayed hyperactivity in rats

Male Wistar rats subjected to repeated restraint stress (1 h per day for 6 days) displayed increasing locomotor horizontal and vertical activity, measured for 1 h in an autotrack actometer 2 days after the last restraint. The administration of L-type Ca2+ channel blocker nifedipine (5 mg/kg i.p.) before each immobilization session completely prevented the stress-related augmentation of the locomotor activity. This shows that functional Ca2+ channels are required for development of stress-related motor activation and suggests that some effects of repeated stress may be prevented by application of Ca2+ channel blockade before stressful stimuli.