Fig. 1.

Effects of early postnatal alcohol exposure on the light-dark entrainment of the rhythm in wheel-running activity. (A) Representative activity records of three adult male rats from the SC, GC, and EtOH groups during entrainment to LD 12:12. Actograms are double-plotted over a 48-hr period. The closed bars at the top and shading on the records signify the timing of the dark phase in the LD 12:12 cycle. (B) During LD 12:12 entrainment, the phase angle between activity onsets and lights-off in EtOH rats (n = 12) was significantly different (*p < 0.05) from that observed in the SC and GC groups (@ n = 12). Bars represent the mean (±SEM) phase angle of entrainment (ψ) to LD 12:12 in minutes. Negative values indicate that daily onsets of activity occur after lights-off, whereas positive values denote that activity onsets precede the end of the light phase. (C) The absolute day-to-day variability in onsets of activity was significantly greater in EtOH rats (*p < 0.01) than in SC and GC animals. Absolute differences in the timing of activity onsets on successive days were analyzed in individual animals, and bars represent mean (± SEM) determinations in minutes.