Fig. 3.

Forced desynchronization of locomotor activity rhythms in OVX+E₂ rats is associated with rhythmic clock gene expression in the vlSCN and dmSCN. A, Representative actogram of an LD22 desynchronized female; arrowheads represent the specific phases at which other individual animals were killed to process their brain for Per1 ISH (n = 2 per time point). B, A χ² periodogram analysis detects two statistically significant rhythmic components of 22 h and 25.08 h in the representative animal shown. C and D, Autoradiographic films of SCN Per1 expression in animals killed on the phases indicated by the triangles in A in a typical desynchronized animal (note that the animal whose actogram is shown was not killed for this experiment). Females killed on aligned days (C) show low levels of Per1 mRNA throughout the SCN during the dark phase and high levels during the light phase. During misaligned days the pattern of expression between the two subregions is 180° out of phase: the dmSCN shows daytime levels of Per1 expression during the subjective day (rest) of the approximately 25-h locomotor activity rhythm, whereas the vlSCN shows daytime levels of Per1 expression during the light phase of the 22-h day (subjective night for the approximately 25 h locomotor activity rhythm). For comparison, the Per1 expression pattern in LD22 desynchronized males is shown (modified from Ref. 26) to convey the similarity between the male and female neural bases of circadian desynchrony.