Studies on the molecular mechanism of sleep

• Main Authors: Yi-Shan Cheng, 鄭亦珊
• Other Authors: Rong-Tsun Wu
• Format: Others
• Language: zh-TW
• Published: 2010
• Online Access: http://ndltd.ncl.edu.tw/handle/64711429465434199926

碩士 === 國立陽明大學 === 生物藥學研究所 === 98 === Mechanism of sleep has yet to be clearly understood, but sleep disorder continues to disturb many people. The predominant hypnotic drugs have many unfavorable side effects and latent risks. This phenomenon have revealed that sleep induced by modulating GABA receptors ligand-gated ion channels is unable to offer the complete functions and effects of sleep. This makes current research seemingly moving away from the major inhibitory GABA receptor system and instead urgently towards modulating more subtle endogenous pathways that controls the sleep–wake cycle. However, Thalidomide, an ideal hypnotic drug evaluated by the clinical report in 1950, may offer some clues to us. This medicine was considered the most effective one that produced restful sleep from which the subject could be aroused readily to a normal state free of ataxia. Thalidomide significantly increased the time spent in REM and SWS as compared with placebo. The effect of thalidomide on REM and SWS is unique compared to other hypnotics: most benzodiazepines and barbiturates decrease REM sleep. In the previous finding of our laboratory, Thalidomide (at 0.1 μg/mL) can reduce cellular bFGF levels effectively. Intravenous injection of 1 mg/kg bFGF to rabbit effectively induced disappearance in the period of REM sleep and a decrease in the period of SWS. Orexinergic system is a network of newly identified neurons and peptides that contribute to wake regulation. The orexins are processed from a common precursor, prepro-orexin and synthesized solely in the lateral hypothalamus and adjacent regions. There was evidence demonstrated that specific neuronal populations within LHA express functional receptors for bFGF. Microinjection of orexin A promotes wakefulness, suppresses SWS and likely defacilitates REM sleep. We supposed that Thalidomide induces sleep through its inhibition of arousal related bFGF and orexinergic system. Our studies revealed 5, 25 mg/kg Thalidomide inhibited prepro-orexin and bFGF mRNA expression while 1 mg /kg bFGF induced prepro-orexin mRNA expression in vivo. 0.1, 1 and 10 μg/ml Thalidomide inhibited prepro-orexin mRNA expression ; 1 and 10 μg/ml Thalidomide inhibited bFGF mRNA expression ex vivo. 1 and 25 ng/ml bFGF induced prepro-orexin mRNA expression ex vivo. 2.5 mg/kg Brotizolam (a benzodiazepine analog) induced bFGF mRNA and prepro-orexin mRNA expression in vivo, the opposite effect compared to Thalidomide. After 6 hours REM sleep deprivation to mice, the levels of bFGF mRNA and prepro-orexin mRNA were increased; and after 2 hours rebound sleep, the levels of bFGF mRNA and prepro-orexin mRNA were reduced. Polysomnography was used to assess the effect of Thalidomide and bFGF on mice sleep. Thalidomide (5, 25 mg/kg) induced an increased in the time spent in NREM sleep and paradoxical sleep, a decreased in wake period. After microinjection of 0.1, 1 and 10 ng bFGF to mice, during 1 hour there was an increased in wake period, disappearance in the period of paradoxical sleep and a decreased in the period of NREM sleep. By these results, Thalidomide inhibited bFGF mRNA and prepro-orexin mRNA expression simultaneously while bFGF induced prepro-orexin mRNA expression. These revealed that Thalidomide may through its inhibition of bFGF to reduce the activity of orexinergic system; and bFGF may plays an important role in arousal mechanism. “Comparison of Thalidomide with Brotizolam” and “REM sleep deprivation” experiments showed that inhibition of bFGF mRNA and prepro-orexin mRNA expression probably involved in the natural sleep mechanism.