Circadian and photic regulation of cryptochrome mRNAs in the rat pineal gland

Expressions of Cry1 and Cry2 mRNA in the rat pineal gland were examined by Northern blot. The levels of Cry1 and Cry2 transcript had a marked circadia n rhythm with peaks at circadian time (CT) 20 in constant darkness. But the amplitude of the Cry1 rhythm was higher than that of the Cry2 rhythm. Furt hermore, a significant increase in Cry1 mRNA levels was caused by light pul se given at CT 16 but not at CT 4, but the expression of Cry2 was not signi ficantly induced by light pulses given at either CT 4 or CT 16. These resul ts suggest that Cry1 in the pineal gland is regulated by photic and circadi an information but Cry2 is only regulated by circadian information. (C) 200 1 Elsevier Science Ireland Ltd and the Japan Neuroscience Society. All righ ts reserved.