Nimodipine maintains in vivo the increase in GFAP and enhances the astroglial ensheathment of surviving motoneurons in the rat following permanent target deprivation.

Abstract

Facial and hypoglossal nerves were resected unilaterally in a total of 108 rats. Rats were divided into two groups; one group received standard food pellets (placebo), the other received food pellets containing the Ca(2+)-blocking agent nimodipine. The expression of glial fibrillary acidic protein was examined in paraffin sections of the brainstem using light microscopical immunocytochemistry, and the degree of glial process ensheathment of the surviving neuronal perikarya in the hypoglossal and facial nuclei quantified on electron micrographs. Up to 28 days post-axotomy no differences in glial fibrillary acidic protein-immunoreactivity were observed between placebo and nimodipine-treated animals. By 42-56 days, glial fibrillary acid protein-immunoreactivity was stronger in the nimodipine treated animals and by 112 days, glial fibrillary acid protein-immunoreactive astrocytes occurred only in nimodipine-treated animals. Thin astrocytic processes were seen to ensheath neurons in both placebo and nimodipine-treated animals. By 28 days post axotomy, lesioned neurons in nimodipine treated animals were covered by a mean of 2.6 (hypoglossal) and 2.9 (facial nucleus) astrocytic lamellae, compared with 1.7 lamellae in the placebo group. This relatively greater ensheathment of hypoglossal and facial neurons was maintained up to 112 days post-lesion, but reduced in the placebo-treated group to approximately 1.4 lamellae. It is concluded that nimodipine enhances the formation of astrocytic lamellae on lesioned neurons and that this process may be associated with a protective role for activated astrocytes directed towards motoneurons suffering from permanent target-deprivation.