Article

Glucocorticoids are not responsible for paradoxical sleep deprivation-induced memory impairments.

Department of Psychobiology, Universidade Federal de São Paulo, São Paulo, Brazil.
Sleep (Impact Factor: 5.1). 05/2008; 31(4):505-15.
Source: PubMed

ABSTRACT To evaluate whether paradoxical sleep deprivation-induced memory impairments are due to release of glucocorticoids, by means of corticosterone inhibition with metyrapone.
The design was a 2 (Groups [control, paradoxical sleep-deprived]) x 2 (Treatments [vehicle, metyrapone]) study, performed in 2 experiments: Acute treatment (single injection given immediately after 96 hours of sleep deprivation) and chronic treatment (8 injections, twice per day, throughout the sleep-deprivation period). Animals were either paradoxical sleep-deprived or remained in their home cages for 96 hours before training in contextual fear conditioning and received intraperitoneal injections of a corticosterone synthesis inhibitor, metyrapone. Memory performance was tested 24 hours after training.
Three-month old Wistar male rats. Measurements: Freezing behavior was considered as the conditioning index, and adrenocorticotropic hormone and corticosterone plasma levels were determined from trunk blood of animals sacrificed in different time points. Animals were weighed before and after the paradoxical sleep-deprivation period.
Acute metyrapone treatment impaired memory in control animals and did not prevent paradoxical sleep deprivation-induced memory impairment. Likewise, in the chronic treatment, paradoxical sleep-deprived animals did not differ from control rats in their corticosterone or adrenocorticotropic hormone response to training, but still did not learn as well, and did not show any stress responses to the testing. Chronic metyrapone was, however, effective in preventing the weight loss typically observed in paradoxical sleep-deprived animals.
Our results suggest that glucocorticoids do not mediate memory impairments but might be responsible for the weight loss induced by paradoxical sleep deprivation.

0 Bookmarks
 · 
97 Views
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The current study investigated the effects of acute versus repeated periods of sleep deprivation on avoidance learning and spatial memory and on the expression of discrete biochemical brain signals involved in stress regulation, motivation and brain plasticity. Male Long–Evans rats were sleep deprived using the platform-over-water method for a single 4 h period (ASD) or for daily 4 h RSD period on five consecutive days (CSD). The Y maze passive avoidance task (YM-PAT) and the Morris water maze (MWM) were used to determine learning and memory 1 h following the last SD period. Region-specific changes in glucocorti-coid receptors (GR), tyrosine hydroxylase (TH), dopamine 1 receptors (DRD1), phospho-CREB (pCREB) and Ki-67 expression were assessed in the hippocampal formation, hypothalamus and mesolimbic regions 72 h following RSD. Behaviorally, our findings revealed increased latency to re-enter the aversive arm in the YM-PAT and reduced distance traveled and latency to reach the platform in the MWM in ASD rats compared to all other groups, indicative of improved avoidance learning and spatial memory, respec-tively. Acute SD enhanced TH expression in the ventral tegmental area, nucleus accumbens and A11 neurons of the hypothalamus and DRD1 expression in the lateral hypothalamus. Cell proliferation in the subventricular zone and pCREB expression in the dentate gyrus and CA3 regions was also enhanced fol-lowing acute SD. In contrast, repeated SD significantly elevated GR-ir at the hypothalamic paraventricular nucleus and CA1 and CA3 layers of the hippocampus compared to all other groups. Our study supports that a brief 4 h sleep deprivation period is sufficient to induce delayed neurochemical changes.
    Behavioural brain research 11/2014; · 3.22 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The introduction and discussion of my thesis, supplemented with references to the published chapters (all freely downloadable) and summaries in Dutch, English, French and German. The discussion contains new data on reversal of the light-dark cycle and on the switch task.
    07/2013, Degree: Ph.D., Supervisor: Eus van Someren
  • [Show abstract] [Hide abstract]
    ABSTRACT: Effects of sleep deprivation (SD) on one-trial recognition memory were investigated in rats using either a spontaneous novel-object or object-place recognition test. Rats were allowed to explore a field in which two identical objects were presented. After a delay period, they were placed again in the same field in which either: 1) one of the two objects was replaced by another object (novel-object recognition); or 2) one of the sample objects was moved to a different place (object-place recognition), and their exploration behavior to these objects was analyzed. Four hours SD immediately after the sample phase (early SD group) disrupted object-place recognition but not novel-object recognition, while SD 4-8h after the sample phase (delayed SD group) did not affect either paradigm. The results suggest that sleep selectively promotes the consolidation of hippocampal dependent memory, and that this effect is limited to within 4h after learning.
    Neuroscience letters. 08/2014;

Full-text

Download
54 Downloads
Available from
May 20, 2014