Rapid eye movement (REM) sleep deprivation reduces rat frontal cortex acetylcholinesterase (EC 3.1.1.7) activity

Abstract

Rapid eye movement (REM) sleep deprivation induces several behavioral changes. Among these, a decrease in yawning behavior produced by low doses of cholinergic agonists is observed which indicates a change in brain cholinergic neurotransmission after REM sleep deprivation. Acetylcholinesterase (Achase) controls acetylcholine (Ach) availability in the synaptic cleft. Therefore, altered Achase activity may lead to a change in Ach availability at the receptor level which, in turn, may result 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 for 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 also used. Achase was measured in the frontal cortex using two different methods to obtain the enzyme activity. One method consisted of the obtention of total (900 g supernatant), membrane-bound (100,000 g pellet) and soluble (100,000 g supernatant) Achase, and the other method consisted of the obtention of a fraction (40,000 g pellet) enriched in synaptic membrane-bound enzyme. In both preparations, REM sleep deprivation induced a significant decrease in rat frontal cortex Achase activity when compared to both home-cage and large platform controls. REM sleep deprivation induced a significant decrease of 16% in the membranebound 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 group 127.9 ± 13.8). There was no difference in the soluble enzyme activity. REM sleep deprivation also induced a significant decrease of 20% in the enriched synaptic membrane-bound Achase activity (home-cage group 126.4 ± 21.5, large platform group 127.8 ± 20.4, REM sleepdeprived group 102.8 ± 14.2). Our results suggest that REM sleep deprivation changes Ach availability at the level of its receptors through a decrease in Achase activity.

Rapid eye movement sleep deprivation induces an increase in acetylcholinesterase activity in discrete rat brain regions

“…Microinjection of carbachol, a cholinergic agonist, into the basal forebrain increases wakefulness, whereas microinjection into the pons induces a state resembling REM sleep (39). We have previously shown a significant decrease in membrane-bound Achase activity in the frontal cortex of REM sleep-deprived rats (12). In the present study there was no difference in Achase activity in the cerebral cortex.…”

“…The frontal cortex receives its cholinergic input from cholinergic neurons located in the rostral nucleus basalis and substantia innominata, whereas the other cortical areas are innervated by cholinergic neurons located more caudally in the nucleus basalis and nucleus of the ansa lenticularis (11). The decrease in Achase activity in the frontal cortex (12) and the lack of change in enzyme activity in the cerebral cortex suggest an effect of REM sleep deprivation on a subpopulation of forebrain basal cholinergic neurons. The pattern of the effect of REM sleep deprivation on Achase activity (decreased activity in frontal cortex with no change in cerebral cortex and increased activity in pons, medulla oblongata and thalamus) seems to represent the functional complexity of cholinergic nuclei in the basal forebrain and brainstem and their role in different brain functions (1,11,36,37,40).…”

“…The control rats were kept individually in their home cages. A large platform control group, to control the stress of the procedure, was not included as it has been shown that there is no change in Achase activity in such groups (7,12).…”

“…Acetylcholinesterase activity was assayed according to Ellman et al (14) as described in detail elsewhere (12). Acetylthiocholine was used as the substrate in a 1-mM final assay concentration.…”

Acetylcholinesterase activity in the pons and medulla oblongata of rats after chronic electroconvulsive shock

“…Homogenates of these brain regions were prepared in cold 0.32 M sucrose and centrifuged in order to obtain membrane-bound and soluble Achase (16). Total (900 g supernatant), membrane-bound (100,000 g sediment) and soluble (100,000 g supernatant) Achase activity was assayed photometrically using acetylthiocholine as the substrate (1 mM final concentration in the assay) as described in detail elsewhere (17). The assay was carried out in the linear range for both protein concentration and incubation time.…”