Disturbances in REM sleep organization can be assessed by measuring its total amount (expressed in minutes or as a percentage of total sleep

time), its onset latency (REM latency), its distribution across the successive non-REM/REM cycles U0126 price during the night, and the actual number of rapid eye movements (REM activity) during this sleep stage or per minute of REM sleep (REM density). For instance, an increased Inhibitors,research,lifescience,medical propensity for REM sleep (or increased REM sleep pressure) is described as a greater amount of REM sleep mostly at the beginning of the night, (also reflected by a shortened REM latency) and an increase in REM activity and REM density. Acetylcholine, MEM sleep, and Alzheimer’s disease At the present, time, there is clear evidence for cholinergic mechanisms in the generation of REM sleep, and this has been the subject of many studies for the last four decades.16-18 Animal studies have demonstrated that the expression of ‘REM sleep-related physiology (eg, thalamocortical arousal, pontogeniculate-occipital waves, Inhibitors,research,lifescience,medical and atonia) depends upon a subpopulation of brain stem pediculopontine tegmental neurons that release acetylcholine to act upon muscarinic receptors.19 Since a variable degree of cell loss in the pediculopontine

region has been reported in Alzheimer’s disease, it, is tempting to speculate that, the Inhibitors,research,lifescience,medical cholinergic deficit induces REM sleep-specific abnormalities such as decreased REM duration and density, increased REM latency, and REM sleep behavior disorder.14, 19 More generally, human studies indicate that acute administration of muscarinic cholinergic agonists increase Inhibitors,research,lifescience,medical REM sleep propensity, whereas acute administration of muscarinic antagonists produce the opposite effect.20 Based upon the pharmacological profile Inhibitors,research,lifescience,medical of the compounds used to manipulate sleep, it appears that both M1 and M2 muscarinic receptor subtypes are involved in REM sleep regulation.20 Regarding acetylcholinesterase

inhibitors, studies in healthy volunteers have shown that physostigmine,21 tacrine,22 and rivastigmine23-24 increase REM sleep pressure. Interestingly, another acetylcholinesterase inhibitor, Methisazone donepezil, may have a role in the treatment of REM sleep behavior disorder,25 a syndrome characterized by the appearance of elaborate motor activity associated with dream mentation due to the intermittent loss of REM sleep muscular atonia. In summary, the study of REM sleep propensity in normal subjects is a particularly useful tool in the development of CNS agents acting on cholinergic neurotransmission. This has been recently exemplified by studies using REM sleep changes as surrogate markers of the activity of acetylcholinesterase inhibitors. Drugs enhancing cholinergic transmission have been consistently demonstrated to increase REM sleep pressure.