Fig 1.
TgCRND8 mice show sleep-wake cycle disruption at early and advanced pathological stages.
Hourly time courses (A) and cumulative percent duration (B and C) of wake, NREM and REM sleep across the light and dark phases at 3 (NTg n = 7, Tg n = 8), 7 (NTg n = 5, Tg n = 7) and 11(NTg n = 6, Tg n = 4) months of age. (B) During the dark phase, 3, 7 and 11-month-old TgCRND8 spend more time awake and less time in NREM sleep in comparison to NTg. Three and 7-month-old TgCRND8 mice also show a significant decrease in the percent time spent in REM sleep during the dark phase in comparison to NTg. (C) During the light phase, 3, 7 and 11-month-old TgCRND8 spend more time awake and less time in NREM sleep in comparison to NTg. Total time spent in REM sleep did not differ significantly between TgCRND8 and NTg during the light phase, at all ages studied. Error bars represent SEM. Panel A was analyzed by two-way ANOVA, followed by Bonferroni test for multiple comparisons. Panels B and C were analyzed by two-way ANOVA, followed by Tukey’s post-hoc test, * P<0.05, ** P<0.01, ***P<0.001.
Table 1.
Average episode duration and number of transitions to wake, NREM sleep and REM sleep during the dark phase (DP) and light phase (LP) in TgCRND8 and NTg mice.
Fig 2.
TgCRND8 mice show alterations in brain oscillatory activity during wakefulness, NREM and REM sleep.
Normalized power spectrums from 0.125–50 Hz during wakefulness (A), NREM (C), and REM sleep (E), and normalized spectral power quantifications of key frequency bands during wakefulness (B), NREM (D) and REM sleep (F) at 3 (NTg n = 7, Tg n = 8), 7 (NTg n = 5, Tg n = 7) and 11 months (NTg n = 6, Tg n = 4). (A and B) During wakefulness, 3-month-old TgCRND8 show a reduction in delta power (0.5–4.5 Hz), and at all ages, higher beta (14–20 Hz) and low gamma power (20–50 Hz) in comparison to NTg. (C and D) at all ages studied, NREM sleep delta power (0.5–4.5 Hz) was preserved in TgCRND8 in comparison to NTg. Seven-month-old TgCRND8 mice showed higher NREM low gamma power (20–50 Hz) in comparison to NTg. (E and F) The REM sleep power spectrum was unaltered in 3-month-old TgCRND8 mice, while 7 and 11-month-old TgCRND8 showed reduced REM sleep theta power (7–10 Hz) in comparison to NTg. Seven-month-old TgCRND8 also show higher REM sleep low gamma power (20–50 Hz) in comparison to NTg. The data represented above include vigilance state spectral power analysis of the dark phase (i.e. active phase) for wakefulness and of the light phase (i.e. resting phase) for NREM and REM sleep. Error bars represent SEM. Two-way ANOVA, followed by Tukey’s post-hoc test. * P<0.05, ** P<0.01, *** P<0.001.
Fig 3.
Three-month-old TgCRND8 mice differ from NTg in their homeostatic response to total sleep deprivation.
Normalized NREM sleep power spectrums from 0.125–40 Hz and quantification of NREM delta power (0.5–4.5 Hz) (A), time spent awake (B), time spent in NREM sleep (C), and time spent in REM sleep (D) under baseline and rebound conditions in 3-month-old NTg (n = 7) and TgCRND8 mice (n = 9). Total sleep deprivation (TSD) was performed for 6 hours, beginning at the onset of the light phase. The rebound period corresponds to the 2-hour period immediately following TSD. (A) Both TgCRND8 and NTg mice show a significant shift towards higher NREM delta power during the rebound period in comparison to baseline. Interestingly, the NREM delta power rebound response was blunted in TgCRND8 mice, with an 18% and 27% increase between baseline and rebound in TgCRND8 and NTg, respectively. (B) TgCRND8 show a significant decrease in time spent awake during the rebound period in comparison to baseline. No significant change in time spent awake during the rebound period in comparison to the baseline period was observed in NTg, and this response did not differ significantly from TgCRND8. (C) TgCRND8 show a significant increase in time spent in NREM sleep during the rebound period in comparison to baseline. No significant change in time spent in NREM sleep during the rebound period in comparison to the baseline was observed in NTg, and this response did not differ significantly from that observed in TgCRND8. (D) TgCRND8 show a significant increase in time spent in REM sleep during the rebound period in comparison to baseline. No significant change in time spent in REM sleep during the rebound period in comparison to the baseline period in NTg, and this response differed significantly from that observed in TgCRND8. Time spent in REM sleep during the rebound period was significantly greater in TgCRND8 in comparison to NTg. Error bars represent SEM. Mixed design two-way ANOVAs followed by simple effects analysis or Tukey’s post hoc where appropriate, * P<0.05, ** P<0.01, *** P<0.001.
Fig 4.
Quantification of Aβ42 levels from key regions regulating the sleep-wake cycle.
Quantification of total Aβ42 levels from the prefrontal cortex, hypothalamus, thalamus and brainstem of 3 (n = 7), 7 (n = 9) and 11-month-old (n = 7) TgCRND8 mice. Picograms (pg) of total Aβ42 are normalized to milligrams (mg) of protein per sample. (A, B and C) At 3, 7 and 11 months of age the prefrontal cortex contains the highest level of total Aβ42, differing significantly from the hypothalamus, thalamus and brainstem. (C) At 11 months of age, the thalamus contains significantly higher total Aβ42 than the brainstem. (D) Progression of total Aβ42 overexpression in the prefrontal cortex, hypothalamus, thalamus and brainstem at 3, 7 and 11 months of age. Error bars represent SEM. Fig 4A, 4B and 4C were analyzed by one-way ANOVA for the effect of brain region at a given age, followed by Tukey’s post-hoc. * Denotes a significant difference between the prefrontal cortex and each other region. # Denotes a significant difference between the thalamus and the brainstem. */# P<0.05, ** P<0.01, *** P<0.001.
Fig 5.
Prazosin differentially affects NREM sleep in 3.5-month-old TgCRND8 and NTg mice.
Time spent in NREM sleep during the 2-hour period following administration of the α1-adrenergic antagonist, prazosin, at 1 (A), 2 (B) and 5 (C) mg/kg versus vehicle in 3.5-month-old NTg and TgCRND8 mice. Prazosin or vehicle was administered at 10:00 AM via an intraperitoneal injection. (A) Treatment with Prazosin at 1 mg/kg does not significantly affect the percent time spent in NREM sleep when compared to vehicle in both NTg and TgCRND8. (B) At 2 mg/kg, treatment with Prazosin significantly increases the time spent in NREM sleep in comparison to vehicle in NTg mice only. The observed increase in NREM sleep in NTg following treatment with 2 mg/kg prazosin differed significantly from time spent in NREM sleep following treatment with 2 mg/kg in TgCRND8. (C) At 5 mg/kg, prazosin significantly increases time spent in NREM sleep in both NTg and TgCRND8 mice. Error bars represent SEM. NTg vehicle n = 11, NTg 1, 2 and 5 mg/kg n = 8, Tg vehicle n = 11, Tg 1 and 2 mg/kg n = 9, Tg 5 mg/kg n = 6. Fig 5A, 5B and 5C were analyzed by individual two-way ANOVAs comparing each prazosin dose to vehicle, followed by Tukey’s post-hoc or simple effects analysis where appropriate, * P<0.05, ** P<0.01, *** P<0.001.
Table 2.
Duration of wake, NREM sleep and REM sleep during the 2 hours following prazosin administration in 3.5-month-old TgCRND8 and NTg mice.