Kinetics of cell proliferation in the postnatal rat dentate gyrus.

Cell cycle parameters in the dentate gyrus of the postnatal rat hippocampus were measured, using the method of percentage labelled mitoses. In animals aged 1, 6 and 12 days, cell cycle times range from 15.1 to 17.7 h, S phase duration from 10.1 to 11.7 h, length of the G2 phase from 2.5 to 3.3 h and G1 from 1.1 to 2.4 h. These figures are similar to those obtained for other precursor cell populations in the brain. On the day after birth the labelling index in the dentate hilus is 4.5% and estimated turnover time 220 h, while on day 6 the labelling index is 3.7% and estimated turnover time 310 h. It is calculated that precursor cells outnumber granule cells by at least 3:1 at birth and 2:1 by day 6.