Fig. 1.

Serotonergic phase advances of the SCN neuronal activity rhythm. Shown are the 2 hr means ± SEM of SCN neuronal activity obtained in a control experiment (A), after treatment with 10 μm 5-HT (B), and after treatment with (+)DPAT (10 μm) (C). Neuronal activity peaked near ZT6 in the control experiment, whereas the peak in neuronal activity occurred at ZT2 after both the 5-HT and (+)DPAT treatment. Thus, both 5-HT and (+)DPAT phase-advanced the neuronal activity rhythm by 4 hr. Horizontal bars, Time of lights-off in the animal colony; vertical bar, time of drug treatment;dotted line, mean time-of-peak in control experiments.