RAPID EYE-MOVEMENT (REM) SLEEP-DEPRIVATION REDUCES RAT FRONTAL-CORTEXACETYLCHOLINESTERASE (EC-3.1.1.7) ACTIVITY

Rapid eye movement (REM) sleep deprivation induces several behavioral changes. Among these, a decrease in yawning behavior produced by low d oses of cholinergic agonists is observed which indicates a change in b rain cholinergic neurotransmission after REM sleep deprivation. Acetyl cholinesterase (Achase) controls acetylcholine (Ach) availability in t he synaptic cleft. Therefore, altered Achase activity may lead to a ch ange in Ach availability at the receptor level which, in turn, may res ult in modification of cholinergic neurotransmission. To determine if REM sleep deprivation would change the activity of Achase, male Wistar rats, 3 months old, weighing 250-300 g, were deprived of REM sleep fo r 96 h by the flower-pot technique (N = 12). Two additional groups, a home-cage control (N = 6) and a large platform control (N = 6), were a lso used. Achase was measured in the frontal cortex using two differen t methods to obtain the enzyme activity. One method consisted of the o btention of total (900 g supernatant), membrane-bound (100,000 g pelle t) and soluble (100,000 g supernatant) Achase, and the other method co nsisted of the obtention of a fraction (40,000 g pellet) enriched in s ynaptic membrane-bound enzyme. In both preparations, REM sleep depriva tion induced a significant decrease in rat frontal cortex Achase activ ity when compared to both home-cage and large platform controls. REM s leep deprivation induced a significant decrease of 16% in the membrane -bound Achase activity (nmol thiocholine formed min(-1) mg protein(-1) ) in the 100,000 g pellet enzyme preparation (home-cage group 152.1 +/ - 5.7, large platform group 152.7 +/- 24.9 and REM sleep-deprived grou p 127.9 +/- 13.8). There was no difference in the soluble enzyme activ ity. REM sleep deprivation also induced a significant decrease of 20% in the enriched synaptic membrane-bound Achase activity (home-cage gro up 126.4 +/- 21.5, large platform group 127.8 +/- 20.4, REM sleep-depr ived group 102.8 +/- 14.2). Our results suggest that REM sleep depriva tion changes Ach availability at the level of its receptors through a decrease in Achase activity.