Nimodipine's protection against corticosterone-induced morphological changes in the hippocampus of young rats

Sustained high levels of corticosterone (CORT), one of the major stress-induced hormones in the rat, were suggested as generating 'accelerated brain aging' and were shown to induce both specific brain changes in the hippocampus and learning impairments in young and middle-aged Fischer-344 rats. Evidence that altered calcium (Ca) homeostasis may play a major role in brain aging has accumulated over the last decade. Recently, new data established a connection between glucocorticoids and voltage-activated Ca influx in aged hippocampal neurons. In the present study, an attempt was made to block the CORT-induced 'accelerated aging' by the simultaneous administration of the L-type Ca channel blocker nimodipine. CORT or placebo sustained-release (SR) pellets were implanted subcutaneously in 3 months old Fischer male rats. Each group was further sub-divided between nimodipine and placebo SR treatments. Characteristic CORT-induced morphological changes were observed in pyramidal hippocampal cells, such as at the CA1 and CA4 sub-regions (22.2%+/-7.7 and 28.6%+/-8.4 of pyknotic cells without clear nuclei, respectively). Concomitant treatment with nimodipine conferred full protection against CORT-induced morphological changes (e.g. 3.2%+/-0.8 and 2.1%+/-1.9 of pyknotic cells in CA1 and CA4, n=7 rats in each group; P <0.04). The neuroprotective efficacy of nimodipine supports the theory of Ca involvement in CORT related 'accelerated brain aging'.