The effect of prolonged gestation on the temporal sequence of cerebellar morphogenesis was studied in rat. Pregnant Holtzman albino rats received daily intramuscular injections of 5 mg progesterone dissolved in sesame oil beginning 1 day before birth (day 21). A second group of pregnant animals received injections of sesame oil, while a third group was untreated. Examination of gross specimens and midsagittal sections of day 25 cerebella (prolonged gestation) from fetuses of progesterone-treated females revealed that folial and fissure development proceeded in a normal fashion when compared to 3 day postpartum controls (groups 2 and 3). Examination of histological sections showed equivalent development with proliferation of external germinal cells, differentiation of basket and internal granule cells, migration of granule cells, elaboration and definition of the molecular layer, and the topographic positioning and growth of Purkinje cells. These results indicate that the temporal sequence involved in the postnatal portion of cerebellar neurogenesis, particularly production of microneurons (granule, basket, stellate), is not triggered by birth. In addition, morphogenetic processes such as cellular proliferation and differentiation, migration of neurons, and the organization as stratification of cerebellar components follows a defined schedule which appears to be independent of the changes accompanying parturition.
All Science Journal Classification (ASJC) codes
- Developmental Neuroscience