Expression of neurofilament immunoreactivity in developing rat cerebellum in vitro and in vivo.

The developmental expression of neurofilaments immunoreactivity was examined in frozen sections and in primary cultures of rat cerebellum by immunocytochemistry with a series of monoclonal antibodies and with a polyclonal antibody. In tissue sections immunocytochemical staining with all the antibodies used was observed in basket cells where adult-like appearance could be detected by 14 days of age and adult-level intensity was achieved by about 25 days. Granule cells remained unstained. Intense staining appeared in cerebellar white matter as early as 7 days after birth. In contrast, neurofilaments immunoreactivity was detected in cultured granule cells from 7-day-old cerebellum. Only polyclonal antibodies reacting with the highly conserved middle alpha-helical domain of the neurofilament subunits were reactive in culture. Staining could be detected in the nerve cell bodies from the first day after plating; thereafter staining intensity increased and was also distributed in neurite extensions. We conclude that unlike their counterparts in vivo cultured embryonic granule cells can express certain neurofilaments immunoreactivity.