Postnatal development of corticosteroid receptor immunoreactivity in the rat cerebellum and brain stem

The postnatal development of corticosteroid receptor immunoreactivity in the rat cerebellum and related brainstem nuclei was studied using a type I receptor antiserum, MINREC4, and a type 11 receptor monoclonal antibody, BUGR2. Type 1 receptor immunoreactive (ir) Purkinje cells were first observed at postnatal day 5 (P5), and increased to adult levels by P20.Type I-ir cells, presumably migrating granule cells, were observed in the developing molecular layer of the cerebellum at P5. By P30, the density of type I-ir cells in the definitive molecular and granular layers was still less than adult levels. In contrast, type I I-ir Purkinje cells were first observed at PI 5 and increased to adult levels by P20. No type I I-ir cells were observed in the proliferative and migratory zones of the molecular layer. By P30, the density of type I I-ir cells in the molecular and granular layers was far less than adult levels. In the deep cerebellar nuclei and most brain stem nuclei type I-ir was observed at P5 and developed to adult levels by P30. Type I I-ir was observed in the deep cerebellar nuclei, red and medial vestibular nuclei by PI5. The pontine and inferior olivary nuclei showed type I I-ir cells by P10. Type I I-ir in these regions developed to adult levels by P30. The earlier development of type I-ir suggests that the type I receptor may mediate the actions of corticosteroids in the cerebellum and related brain stem nuclei during early postnatal life. Both type I and type II corticosteroid receptors may mediate corticosteroid effects in the cerebellum and brain stem nuclei during late postnatal life and adulthood.