The investigation of the embryonic development of the cerebellum has a long history. The postnatal normal development of the cerebellum in rodents and other animals became a popular topic for morphological investigations nearly a century ago. However, surprisingly, only a few studies are available regarding the prenatal normal development of the rodent cerebellum, especially in guinea pigs. Cell proliferation is essential for the development of the nervous system. The assessment of cell proliferation can be achieved by using various methods. In this study, we investigated the cell proliferation of the cerebellar cortex in guinea pigs at different stages of pregnancy and in postnatal life. Fetuses were obtained by cesarean section at 50 or 60 days of gestation (dg). Immunohistochemistry was performed with proliferating cell nuclear antigen (PCNA) antibody in the cerebellum. Strong PCNA immunoreactivity was observed in the external granular layer (EGL), which is a neurogenic zone in the cerebellum. The proportion of PCNA-IR cells was greater at 1 week than at 60 dg in lobule I, but not lobule VIII. After 50 dg, the width of the EGL continued to decline until 1 week, due to the maturation of the EGL cells. These results demonstrate the pattern of PCNA immunoreactivity in the developing cerebellum of guinea pigs. This serves as a guideline to study abnormal cerebellum development.

Introduction
 Materials and Methods
  Animals
  Tissue preparation
  Immunohistochemistry
  Quantitative Analysis
  Statistical analysis
 Results
  Prenatal and postnatal development of guinea pig
  The proportion of PCNA-IR cells to the total cell number in the EGL
  Thickness of the cerebellar cortex
  PCNA immunoreactivity
 Discussion
 Conclusion
 References

• Dong-joon Kim(Department of anesthesiology and pain medicine, Chosun University Hospital)
• Yonghyun Jun(Department of Anatomy, School of Medicine, Chosun University) Correspondence to