CELLULAR CONSTRUCTION OF A CIRCADIAN CLOCK - PERIOD DETERMINATION IN THE SUPRACHIASMATIC NUCLEI

The circadian clock in the suprachiasmatic nuclei is composed of multi ple, single-cell circadian oscillators (clock cells). We now test the hypothesis that the circadian period in behavior is determined by the mean period that arises from the coupling of clock cells with diverse circadian periods. For these studies, we monitored firing rate rhythms of individual suprachiasmatic nuclei neurons on fixed multielectrode plates and exploited the altered circadian periods expressed by hetero zygous and homozygous tau mutant hamsters. The results show that circa dian period in the whole animal is determined by averaging widely disp ersed periods of individual clock cells. The data also demonstrate tha t the tau mutation affects circadian function in a cell-autonomous man ner.