文章作者 100test 发表时间 2007:05:02 14:49:14
来源 100Test.Com百考试题网
a ains of mice. "In general," they reported, "the ability of the compounds to compete at the receptors(40) correlates with their ability to stimulate locomotion in the mouse. i.e., the higher their capacity to bind at the receptors, the higher their ability to stimulate locomo-tion." Theophylline, a close structural relative of caffeine and the major stimulant in tea, was one of the most(45) effective compounds in both regards. There were some apparent exceptions to the general correlation observed between adenosine-receptor binding and stimulation. One of these was a compound called 3-isobuty1-1-methylxanthine(IBMX), which bound very(50) well but actually depressed mouse locomotion. Snyder et al suggest that this is not a major stumbling block to their hypothesis. The problem is that the compound has mixed effects in the brain, a not unusual occurrence with psychoactive drugs. Even caffeine, which is generally(55) known only for its stimulatory effects, displays this property, depressing mouse locomotion at very low concentrations and stimulating it at higher ones.
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