sentences:  Histamine has an excitatory effect in the brain via H1 receptors in the cerebral cortex, and so drugs such as ciproxifan which block the H3 receptor and consequently allow more histamine to be released have an alertness-promoting effect.Ciproxifan produces wakefulness and attentiveness in animal studies, and produced cognitive enhancing effects without prominent stimulant effects at relatively low levels of receptor occupancy, and pronounced wakefulness at higher doses.It has therefore been proposed as a potential treatment for sleep disorders such as narcolepsy and to improve vigilance in old age, particularly in the treatment of conditions such as Alzheimer's disease.