Asymmetrical electrical activity between the suprachiasmatic nuclei in vitro

In order to test the hypothesis that each side of the suprachiasmatic nuclei (SCN) contains independent circadian oscillators, pairs of cells were recorded from contralateral SCN alternating each nucleus, in hypothalamic slices prepared for extracellular single unit recording. The analysis was made by separating the data from right and left nuclei. Circadian variations in the electrical activity of neurones were present in either side of the SCN. The right SCN presented a bimodal waveform, without apparent change of phase between slices prepared from animals under LD or DD. In contrast, the fluctuations of the left SCN were unimodal in slices of both groups. There was also a difference of 2 h in the interval of maximal activity between the groups from LD and DD. These asymmetrical wave forms are consistent with previous studies suggesting that the contralateral SCN may act as independent oscillators.