Diversity in the circadian periods of single neurons of the rat suprachiasmatic nucleus depends on nuclear structure and intrinsic period.

The circadian periods of single cultured neurons of the hypothalamic suprachiasmatic nucleus (SCN) in rats were assessed by means of multi-electrode array dish. Although the mean circadian period was not different between the dispersed cell culture and organotypic slice culture, the periods distributed in a wide range from 20.0 to 30.9 h in the former whereas concentrated in a narrow range in the latter. The same difference was also detected within each culture dish. There is a significant correlation between the period length and variation of circadian rhythm, where the more the mean circadian period in a culture dish deviates from the overall mean, the larger the standard deviation of period in a dish becomes. Such a correlation was not observed in the organotypic slice culture. These findings indicate that the diversity of circadian periods in the individual SCN neurons depends on the maintenance of SCN structure and the circadian period, suggesting that not only cell-to-cell communication but also the intrinsic circadian period plays a significant role in synchronizing the constitutional oscillators in the SCN.