DIFFERENTIAL EXPRESSION OF CALBINDIN AND CALMODULIN IN MOTONEURONS AFTER HYPOGLOSSAL AXOTOMY

Axotomy induces a profound modification of Ca2+ homeostasis in injured neurons which may lead to neuronal death. Remarkably, after axotomy a nd resection of the hypoglossal nerve, 65-75% of the hypoglossal moton eurons survive in the long term and this suggests some adaptive mechan isms compensating the massive calcium influx. As potential components of this adaptation, we have examined calmodulin and calbindin-D-28k by in situ hybridisation and immunohistochemistry in motoneurons of the rat after hypoglossal nerve transection. Neuronal calbindin mRNA and p rotein content was low in normal state, transiently increased to 200% of the basal expression at 8 days post-operation (dpo), then declined to normal again until 28 dpo. Calmodulin mRNA was highly expressed in normal hypoglossal motoneurons and remained constant after axotomy. Ca lmodulin protein immunoreactivity, however, was transiently decreased in axotomised motoneurons suggesting post-transcriptional modification . The upregulation of calbindin expression may facilitate the survival of injured motoneurons. (C) 1998 Elsevier Science B.V.