Granule neuron DNA damage following deafferentation in adult rats cerebellar cortex: A lesion model

Neuronal programmed cell death is regulated by a neurotrophic supply from t argets and afferent inputs. The relative contribution of each component var ies according to neuronal type and age. We have previously reported that pr imary cultures of cerebellar granule cells undergo apoptosis when deprived of depolarising KCI concentrations, suggesting a significant role of affere nt inputs in the control of cerebellar granule cells survival. This issue w as investigated by setting up various in vivo lesional paradigms in order t o obtain partial or total deafferentation of the cerebellar granule layer i n adult rats. At different times after surgery, cerebellar sections were su bjected to TUNEL staining in order to detect possible DNA damage. One week after unilateral pedunculotomy, few scattered groups of apoptotic granule n eurons were observed in the homolateral hemisphere. On the contrary, total deafferentation obtained by a new experimental paradigm based on an "L-cut" lesion induced massive and widespread apoptotic death in the granule layer of the deafferentated area. The time window of DNA fragmentation in granul e layer was one to seven days after the "L-cut". Selective Purkinje cell de afferentation obtained by 3-acetylpyridine injection did not result in TUNE L staining in the cerebellar cortex. The current finding that mossy fiber axotomy induces granule cell apoptotic death points out for the first time the crucial role of afferent inputs in mature granule cell survival. Moreover, the in vivo lesional model describ ed here may prove to be an useful tool for investigating cellular and molec ular mechanisms of neuronal death triggered by deafferentation. (C) 1999 IB RO. Published by Elsevier Science Ltd.