The acetylcholinesterase inhibitor di-isopropyl-fluorophosphate increases REM sleep in rats

In this experiment, rats were treated chronically with moderate doses of the acetylcholinesterase inhibitor di-isopropyl-fluorophosphate (DFP). After an initial injection of 1.0 mg/kg DFP, the rats received a 0.5 mg/kg injection every third day thereafter for a total of 5 injections (13 days). Following the treatment regimen, the rats were found to have increased amounts of REM sleep compared to vehicle control rats. The time spent awake and in slow wave sleep was relatively unaffected. The increase in REM sleep appears to be due to increased numbers of REM sleep episodes and not an increase in the average length of the REM sleep episodes. Furthermore, the increased REM sleep does not appear to be due to REM rebound or to disruptions of circadian rhythm.