NIMODIPINE COUNTERACTS CORTICOSTERONE-INDUCED HABITUATION IMPAIRMENTS

Corticosterone or placebo sustained-release pellets (4 pellets of 200 mg each, released over 90 days) were implanted subcutaneously in young Fischer-344 rats, fed with either regular food or with food containin g 860 ppm of nimodipine. Following 2 weeks of treatment, the habituati on of the rats to a new environment was studied. On the first test day , placebo-implanted rats explored the new environment and exhibited a characteristic habituation. On the second test day, 48 hr later, low a ctivity was measured in the already familiar environment. This habitua tion was absent in corticosterone-implanted rats fed with regular food . However, corticosterone-implanted rats fed with food containing nimo dipine behaved during the second test similarly to the placebo-implant ed group. The data indicated that the behavioral deficit, induced in F ischer-344 rats by the high corticosterone levels, was reversed by the nimodipine treatment. Thus, nimodipine may be useful in counteracting certain prolonged stress-related cognitive impairments. (C) 1995 Acad emic Press, Inc.