Circadian rhythms and light responses of clock gene and arylalkylamine N-acetyltransferase gene expressions in the pineal gland of rats
Wang Guoqing, Du Yuzhen, Tong Jian
Department of Toxicology, School of Radiation Medicine & Public Health, Soochow University.Suzhou 215007,Jiangsu
Abstract
This study was to investigate the circadian rhythms and light responses of Clock gene and arylalkylamine N-acetyltransferase (NAT) gene expressions in the rat pineal gland under the 12 h-light : 12 h–dark cycle condition (LD) and constant darkness (DD). Sprague-Dawley rats housed under the light regime of LD (n=36) for 4 weeks and of DD (n=36) for 8 weeks were sampled for the pineal gland once a group (n=6) every 4 hours in a circadian day. The total RNA was extracted from each sample and the semiquantitative reverse transcription polymerase chain reaction (RT-PCR) was used to determine the temporal changes in mRNA levels of Clock and NAT genes during different circadian times or zeitgeber times. The data were analysed by the cosine function software, Clock Lab software and the amplitude F test was used to reveal the circadian rhythm. The main results obtained are as follows. (1) In DD or LD condition, both of Clock and NAT mRNA levels in the pineal gland showed robust circadian oscillation (P < 0.05) with the peak at the subjective night or at night-time. (2) In comparison with DD regime, the amplitudes and the mRNA levels at peaks of Clock and NAT expressions in LD in the pineal gland were significantly reduced (P < 0.05). (3) In DD or LD condition, the circadian expressions of NAT were similar in pattern to those of Clock in the pineal gland (P > 0.05). These findings suggest that the expressions of Clock and NAT genes in the pineal gland not only show remarkably synchronous endogenous circadian rhythmic changes, but also response to the ambient light signal in a reduced manner.
Key words: Clock gene;Arylalkylamine N-acetyltransferase gene;Circadian rhythm;Light;Pineal gland
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Citing This Article:
Wang Guoqing, Du Yuzhen, Tong Jian. Circadian rhythms and light responses of clock gene and arylalkylamine N-acetyltransferase gene expressions in the pineal gland of rats. Acta Physiol Sin 2005; 57 (1): (in Chinese with English abstract).