Postnatal growth and development of the gerbil brain

The Mongolian gerbil brain undergoes most of its postnatal growth and development during the first 2 weeks of life. At birth the gerbil weighs only 4% of its adult body weight, and the cerebrum and cerebellum are only 24 and 9.9%, respectively, of their adult weights. The cerebrum is more mature at birth than is the cerebellum. At 7 days of age, the cerebrum contains 55.7% of its adult DNA content, whereas the cerebellum has amassed only 17.2% of its adult content. By 21 days of age, cerebral growth is essentially complete, as measured by DNA, RNA, and protein accumulation. Cholesterol content approaches adult values in the cerebrum by 60 days of age. The rate of growth of the cerebrum and rate of RNA accumulation peak at 7 to 8 days of age. The cerebral protein velocity curve reaches its maximum at 10 to 11 days, that of DNA at 12 days, and cholesterol at 17 days of age. Conversely, the cerebellum at 21 days of age has only 65.6% of its adult protein content and 77.4% of its adult weight, although DNA multiplication is nearly complete. Myelination, as measured by accumulation of cholesterol, is not complete until sometime between 90 and 180 days of age. The velocity maxima of the other cerebellar constituents occur at about 12 to 13 days of age.