Fig. 3.

Induction of circadian clock genes in SCN of phase-shifted mice. Representative dark-field autoradiograms ofin situ hybridization. A,mPer and mCry1 expression in mice entrained to 12L:12D and sampled in darkness 1(mPer1) or 3 hr (mPer2, mCry1) after lights-off, or after acute 6 hr phase advance of the L:D cycle. b,mPer2 and mCry1 expression 3 d after a 6 hr advance, sampled 2, 12, or 17 hr after lights-on. Note dissociation of Per and Cry expression. Images are derived from the same animal at each time. c,mPer and mCry1 expression in mice subjected to an acute 6 hr delay of the light/dark cycle. Mice were sampled in darkness at ZT18 or after 6 hr of light exposure between former ZT12 to ZT18. Note coordinate upregulation of bothmPer2 and mCry1 mRNA. Induction tomPer1 was weak and restricted to the ventral SCN. Images for the three mRNAs are derived from the same animal at either time. Representative coronal sections immunostained for mPER or mCRY.d, Mice entrained to 12L:12D, sampled at ZT02, or subjected to an acute 6 hr phase advance to lights-on (now on at original ZT18) and sampled after 8 hr of illumination (new ZT08).e, Mice entrained to 12L:12D, sampled at ZT22, or subjected to an acute 6 hr phase delay (lights now off at original ZT18) and sampled 4 hr after the end of illumination (original ZT22, new ZT16).