TRANSIENT C-FOS GENE-EXPRESSION IN CEREBELLAR DEVELOPMENT AND FUNCTIONAL STIMULATION

This study examined the temporal appearance of c-fos expression in rat cerebella from birth to postnatal day 21 (P21) and following systemic kainic acid administration in adults. During development, Fos positiv e granule cells appeared first at P3 in caudal lobules and extended to all folia by P9. These reactive cells occurred in clusters throughout the granular layer and reached their highest reactivity by P15. In ad dition, Fos positive basket and stellate cells were seen in the molecu lar layer at this time. A steep decline in Fos protein labeling of the cerebellum began by P18 and was barely detectable in adulthood. In ad ult rats, systemic injection of kainic acid induced c-fos expression i n granule cells and stellate/basket interneurons within 1 h of treatme nt. Fos reactive granule cells appeared in clusters with some forming distinct parasagittal bands in caudal folia. One day after unilateral cerebellar lesioning, a limited number of reactive cells were found on the lesion margins. A combination of lesioning and systemic kainic ac id produced a strong, c-fos expression throughout the ipsilateral gran ular layer as well as in Purkinje cell nuclei. Contralateral to the le sion, the pattern of granule cell reactivity appeared the same but sli ghtly stronger than those with kainate alone. We conclude that c-fos g ene expression occurs transiently in granule cells during postnatal de velopment and can be rapidly re-induced in the adult following systemi c injection of glutamate agonists. The c-fos expression patterns sugge st that subpopulations of granule cells are clustered and related to t he parasagittal compartments of Purkinje cells. (C) 1998 Elsevier Scie nce B.V. All rights reserved.