Objective This study was designed to study the distribution and developmental changes of 11?\|hydroxysteroid dehydrogenase 1(11?\|HSD1) in the neonatal rat brain. Methods Immunohistochemistry and Western blot were used to observe the distribution and changes of 11?\|HSD1 protein levels in the neonatal rat brain. Results 11?\|HSD1 protein was highly expressed in all layers of the cerebral cortex as well as all sub\|regions of the hippocampus by immunohistochemistry.Western blot analysis showed that the expression of 11?\|HSD1 protein in the neonatal rat cortex,hippocampus and hypothalamus was higher during the first two weeks of life,but started to fall from 15th day after birth.Conclusion\ The expression pattern of 11?\|HSD1 protein in different brain areas in the neonatal rat suggests that 11?\|HSD1 protein may play an important role in the development and maturation of the brain.\;[