High resolution

Module 6: Figure firing rates of SCN neurons

Firing rate of suprachiasmatic nucleus (SCN) neurons recorded during either the day or night.

Suprachiasmatic nucleus (SCN) neurons prepared from rats during the day had a lower membrane potential than that found for neurons during the night. The former also had a much higher frequency of spontaneous action potentials (4 Hz) than those recorded during the night phase (0.4 Hz). When cells were treated with tetrodotoxin (TTX), action potentials disappeared in both cases. However, the day cells were left with a slow oscillation of membrane potential which had a frequency similar to that recorded for the action potentials. The nature of this membrane oscillator may provide clues about how the circadian oscillator communicates with the plasma membrane, as discussed in the text. Reproduced by permission from Macmillan Publishers Ltd: Nature, Pennartz, C.M.A., de Jou, M.T.G., Bos, N.P.A., Schaap, J. and Geurtsen, A.M.S. (2002). Diurnal modulation of pacemaker potentials and calcium current in the mammalian circadian clock. 416:286–290. Copyright (2002); http://www.nature.com; see Pennartz et al. 2002.