[Circadian rhythms and light responses of clock gene and arylalkylamine N-acetyltransferase gene expressions in the pineal gland of rats].

Both Clock and NAT gene expressions in the rat pineal gland exhibit robust circadian oscillation with peaks at night-time.

• The mRNA levels of Clock and NAT genes showed significant rhythmic changes under both light-dark and constant darkness conditions (P<0.05).
• In the light-dark cycle, the amplitudes and peak mRNA levels of Clock and NAT genes were significantly lower compared to those in constant darkness (P<0.05).
• The circadian expression patterns of the NAT gene were similar to those of the Clock gene in the pineal gland (P>0.05).
• These findings indicate that Clock and NAT genes respond to light signals, albeit in a diminished manner.

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