Saturday, March 07, 2015

Inhibition of Hippocampal Neurogenesis by Sleep Deprivation is Independent of Circadian Disruption and Melatonin Suppression

Dean Reinke
Deans’ Stroke Musing
Monday, July 25, 2011

I know that for 4 years after my event I was not sleeping well, sleep apnea - still unresolved, no dreaming - resolved by moving my statin and anti-depressant pills to the morning from the evening. Of course I should not have done this without talking to my doctor but hell I know more that he does how various pills affect me. Inhibition of Hippocampal Neurogenesis by Sleep Deprivation... I'm still sleep-deprived but it is better.


Procedures that restrict or fragment sleep can inhibit neurogenesis in the hippocampus of adult rodents, although the underlying mechanism is unknown. We showed that rapid-eye-movement sleep deprivation (RSD) by the platform-over-water method inhibits hippocampal cell proliferation in adrenalectomized rats with low-dose corticosterone clamp. This procedure also greatly disrupts daily behavioral rhythms. Given recent evidence for circadian clock regulation of cell proliferation, we asked whether disruption of circadian rhythms might play a role in the anti-neurogenic effects of sleep loss. Male Sprague–Dawley rats were subjected to a 4-day RSD procedure or were exposed to constant bright light (LL) for 4 days or 10 weeks, a non-invasive procedure for eliminating circadian rhythms of behavior and physiology in this species. Proliferating cells in the granule cell layer of the dentate gyrus were identified by immunolabeling for the thymidine analogue 5-bromo-2-deoxyuridine. Consistent with our previous results, the RSD procedure suppressed cell proliferation by not, vert, similar 50%. By contrast, although LL attenuated or eliminated daily rhythms of activity and sleep–wake without affecting daily amounts of REM sleep, cell proliferation was not affected. Melatonin, a nocturnally secreted neurohormone that is inhibited by light, has been shown to promote survival of new neurons. We found that 3-weeks of LL eliminated daily rhythms and decreased plasma melatonin by 88% but did not significantly affect either total cell survival or survival of new neurons (doublecortin+). Finally, we measured cell proliferation rates at the beginning and near the end of the daily light period in rats entrained to a 12:12 light/lark (LD) cycle, but did not detect a daily rhythm. These results indicate that the antineurogenic effect of RSD is not secondary to disruption of circadian rhythms, and provide no evidence that hippocampal cell proliferation and survival are regulated by the circadian system or by nocturnal secretion of pineal melatonin.


▶ Constant light suppresses daily sleep rhythms and plasma melatonin in rats.
▶ Four days of REM-sleep deprivation decreases hippocampal cell proliferation by not,
    vert, similar 50%.
▶ Constant light for 4 days or 10 weeks does not affect hippocampal cell proliferation.
▶ Constant light for 3 weeks does not affect hippocampal cell survival.
▶ Proliferation does not vary between the beginning and end of the daily sleep phase.

Key words: neurogenesis; sleep deprivation; hippocampus; melatonin; circadian rhythms; constant light

Abbreviations: BrdU, 5-bromo-2′-deoxyuridine; CORT, corticosterone; CV, coefficients of variation; DAB, diaminobenzidine tetrahydrochloride; DCX, doublecortin; EEG, electroencephalogram; GCL, granule cell layer; LD, light/lark; LL, constant bright light; NREM, none-rapid-eye-movement; PB, phosphate buffer; PBS, phosphate buffered saline; RSD, rapid-eye-movement sleep deprivation; SD, sleep deprivation; SGZ, subgranular zone; TBS, Tris-buffered saline; ZT, zeitgeber time

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