CIRCADIAN PERIODS OF SINGLE SUPRACHIASMATIC NEURONS IN RATS

Neuronal activity of a single neuron was monitored continuously for mo re than 5 days by means of a multi-electrode dish in dispersed cell cu lture of the rat suprachiasmatic nucleus (SCN). Sixty-seven out of 88 neurons showed a robust circadian rhythm in firing rate. The mean circ adian period was 24.2 h, which was almost identical to that of the loc omotor activity rhythm in 114 weanling rats blinded on the day of birt h. However, the circadian period in individual SCN neurons was scatter ed from 20.0 to 28.3 h (SD, 1.4 h), while the period of activity rhyth m clustered from 24.0 to 24.8 h (SD, 0.2 h). It is concluded that a la rge number of SCN neurons contain the circadian oscillator, the period of which is more variable than the circadian period of the SCN as a w hole. It is suggested that the circadian rhythms in individual SCN neu rons are capable of synchronizing to each other and are integrated to constitute a multiple oscillator system(s) within the SCN. (C) 1998 El sevier Science ireland Ltd. All rights reserved.